/* assets/style.css - PHP Chat */
* { box-sizing: border-box; margin: 0; padding: 0; }

[data-theme="dark"] {
    --bg: #0f1419;
    --bg-2: #161b22;
    --bg-3: #1f2630;
    --bg-hover: #2a3340;
    --border: #2a3340;
    --border-strong: #3a4452;
    --text: #e6edf3;
    --text-dim: #8b949e;
    --accent: #2f81f7;
    --accent-hover: #4493f8;
    --danger: #f85149;
    --success: #3fb950;
    --warning: #d29922;
    --code-bg: #0d1117;
    --pin: #ffd33d;
    --shadow: rgba(0,0,0,0.4);
}

[data-theme="light"] {
    --bg: #f5f7fa;
    --bg-2: #ffffff;
    --bg-3: #eef2f7;
    --bg-hover: #e2e8f0;
    --border: #d4dae3;
    --border-strong: #b8c0cd;
    --text: #1a2332;
    --text-dim: #5e6878;
    --accent: #1f6feb;
    --accent-hover: #2f81f7;
    --danger: #d1242f;
    --success: #1a7f37;
    --warning: #9a6700;
    --code-bg: #f6f8fa;
    --pin: #d4a017;
    --shadow: rgba(0,0,0,0.08);
}

html, body {
    height: 100%;
    background: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    font-size: 14px;
    line-height: 1.5;
}

.app { display: grid; grid-template-columns: 1fr 340px; height: 100vh; }

.chat-main {
    display: flex; flex-direction: column;
    background: var(--bg);
    overflow: hidden;
    border-right: 1px solid var(--border);
}

/* Messages có padding ngang để không sát mép */
.messages {
    flex: 1; overflow-y: auto;
    padding: 16px 32px;
    display: flex; flex-direction: column; gap: 8px;
}

/* Khoảng đệm cho input area */
.input-area {
    border-top: 1px solid var(--border);
    background: var(--bg-2);
    padding: 12px 32px;
    display: flex; gap: 8px; align-items: flex-end;
}

.reply-preview, .pending-attachments {
    padding-left: 32px;
    padding-right: 32px;
}

/* ========== Header ========== */
.chat-header {
    padding: 10px 16px;
    background: var(--bg-2);
    border-bottom: 1px solid var(--border);
    display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
}
.chat-header h1 { font-size: 16px; font-weight: 600; }
.chat-header .badge { color: var(--text-dim); font-size: 11px; }
.chat-header .spacer { flex: 1; }

.btn {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 13px;
    transition: background 0.15s, border-color 0.15s;
    display: inline-flex; align-items: center; gap: 6px;
    font-family: inherit;
}
.btn:hover { background: var(--bg-hover); border-color: var(--border-strong); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: white; }
.btn-primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn-danger  { background: var(--danger); border-color: var(--danger); color: white; }
.btn-danger:hover  { background: var(--danger); filter: brightness(1.1); }
.btn-sm { padding: 4px 9px; font-size: 12px; }

/* ========== Time-filter bar ==========*/
.filter-bar {
    background: var(--bg-2);
    border-bottom: 1px solid var(--border);
    padding: 6px 16px;
    display: flex;
    align-items: center;
    gap: 6px;
    flex-wrap: wrap;
    font-size: 12px;
}
.filter-bar .label { color: var(--text-dim); margin-right: 4px; }
.filter-chip {
    padding: 4px 10px;
    border-radius: 14px;
    background: var(--bg-3);
    border: 1px solid var(--border);
    cursor: pointer;
    font-size: 12px;
    color: var(--text);
    font-family: inherit;
}
.filter-chip:hover { background: var(--bg-hover); }
.filter-chip.active { background: var(--accent); border-color: var(--accent); color: white; }
.filter-chip.custom-active { background: var(--accent); border-color: var(--accent); color: white; }
.custom-range {
    display: none;
    align-items: center;
    gap: 4px;
    margin-left: 4px;
}
.custom-range.show { display: inline-flex; }
.custom-range input[type="date"] {
    padding: 3px 6px;
    background: var(--bg-3);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text);
    font-size: 12px;
    color-scheme: light dark;
}

/* ========== Pinned bar ========== */
.pinned-bar {
    background: var(--bg-2);
    border-bottom: 1px solid var(--border);
    padding: 0;
    display: none;
    position: relative;
}
.pinned-bar.has { display: block; }
.pinned-bar-head {
    padding: 8px 16px;
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-size: 13px;
    border-left: 3px solid var(--pin);
}
.pinned-bar-head:hover { background: var(--bg-3); }
.pinned-bar-head .pinned-label {
    color: var(--pin);
    font-weight: 600;
    flex-shrink: 0;
}
.pinned-bar-head .pinned-text {
    color: var(--text-dim);
    overflow: hidden; white-space: nowrap; text-overflow: ellipsis;
    flex: 1;
}
.pinned-bar-head .arrow {
    color: var(--text-dim);
    transition: transform 0.2s;
    font-size: 11px;
}
.pinned-bar.open .pinned-bar-head .arrow { transform: rotate(180deg); }

.pinned-list {
    display: none;
    max-height: 300px;
    overflow-y: auto;
    border-top: 1px solid var(--border);
}
.pinned-bar.open .pinned-list { display: block; }
.pinned-item {
    padding: 8px 16px;
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    border-bottom: 1px solid var(--border);
    font-size: 13px;
}
.pinned-item:last-child { border-bottom: none; }
.pinned-item:hover { background: var(--bg-3); }
.pinned-item .icon { color: var(--pin); flex-shrink: 0; }
.pinned-item .text {
    flex: 1;
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
    color: var(--text);
}
.pinned-item .when {
    color: var(--text-dim);
    font-size: 11px;
    flex-shrink: 0;
}

/* ========== Selection bar ========== */
.selection-bar {
    background: var(--accent);
    color: white;
    padding: 8px 16px;
    display: none;
    align-items: center;
    gap: 12px;
    font-size: 13px;
}
.selection-bar.active { display: flex; }
.selection-bar .btn {
    background: rgba(255,255,255,0.15);
    border-color: rgba(255,255,255,0.3);
    color: white;
}
.selection-bar .btn:hover { background: rgba(255,255,255,0.25); }

/* ========== Messages list ========== */
.messages::-webkit-scrollbar { width: 8px; }
.messages::-webkit-scrollbar-track { background: var(--bg); }
.messages::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 4px; }

.msg {
    background: var(--bg-2);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 10px 12px;
    position: relative;
    max-width: 85%;
    min-width: 250px;
    align-self: flex-start;
    word-wrap: break-word;
    transition: background 0.2s;
}
.msg:hover { background: var(--bg-3); }
.msg.selected { background: rgba(47, 129, 247, 0.15); border-color: var(--accent); }
.msg.pinned {
    border-left: 3px solid var(--pin);
}
.msg.pinned::after {
    content: '📌';
    position: absolute;
    top: 6px;
    right: 8px;
    font-size: 12px;
    opacity: 0.85;
}
.msg.highlight { animation: flash 1.5s ease; }
@keyframes flash {
    0%   { background: rgba(255, 211, 61, 0.4); }
    100% { background: var(--bg-2); }
}

.msg-head {
    display: flex; align-items: center; gap: 8px;
    margin-bottom: 4px;
    font-size: 11px;
    color: var(--text-dim);
}

/* Action buttons - LUÔN HIỆN, không cần hover */
.msg-actions {
    position: absolute;
    top: 6px;
    right: 6px;
    display: flex;
    gap: 2px;
    background: transparent;
    z-index: 1;
}
.msg.pinned .msg-actions { right: 28px; } /* dịch sang trái để chừa chỗ icon ghim */

.msg-actions button {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text-dim);
    cursor: pointer;
    padding: 3px 6px;
    border-radius: 4px;
    font-size: 12px;
    transition: all 0.15s;
}
.msg-actions button:hover {
    background: var(--bg-hover);
    color: var(--text);
}
.msg-actions button.danger:hover { color: var(--danger); }
.msg-actions button.pin-btn:hover, .msg-actions button.pin-btn.active { color: var(--pin); }
.msg-actions button.reply-btn:hover { color: var(--accent); }

.msg-checkbox {
    position: absolute;
    top: 12px; left: -28px;
    width: 18px; height: 18px;
    cursor: pointer;
    accent-color: var(--accent);
    display: none;
}
body.select-mode .msg-checkbox { display: block; }
body.select-mode .msg { margin-left: 30px; }

.reply-snapshot {
    background: rgba(47, 129, 247, 0.1);
    border-left: 3px solid var(--accent);
    padding: 6px 8px;
    border-radius: 4px;
    margin-bottom: 6px;
    font-size: 12px;
    color: var(--text-dim);
    cursor: pointer;
}
.reply-snapshot:hover { background: rgba(47, 129, 247, 0.2); }
.reply-snapshot strong { color: var(--accent); }

.msg-content { white-space: pre-wrap; word-break: break-word; }
.msg-content a { color: var(--accent); text-decoration: none; word-break: break-all; }
.msg-content a:hover { text-decoration: underline; }
.msg-content img.inline-img {
    max-width: 100%; max-height: 320px;
    border-radius: 6px; margin-top: 6px;
    display: block; cursor: pointer;
}

/* ========== Code block ========== */
.code-block {
    background: var(--code-bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    margin: 6px 0;
    overflow: hidden;
}
.code-head {
    background: var(--bg-3);
    padding: 4px 10px;
    display: flex; align-items: center; justify-content: space-between;
    border-bottom: 1px solid var(--border);
    font-size: 11px;
    color: var(--text-dim);
}
.code-head .lang { text-transform: uppercase; font-weight: 600; letter-spacing: 0.5px; }
.code-head .actions { display: flex; gap: 4px; }
.code-head .btn-sm-code {
    background: transparent;
    color: var(--text-dim);
    border: none; cursor: pointer;
    padding: 3px 8px; border-radius: 4px;
    font-size: 11px;
    font-family: inherit;
}
.code-head .btn-sm-code:hover { background: var(--bg-hover); color: var(--text); }
.code-block pre {
    padding: 10px 12px;
    overflow-x: auto;
    font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
    font-size: 12.5px;
    line-height: 1.5;
    color: var(--text);
    background: var(--code-bg);
}
.code-block pre::-webkit-scrollbar { height: 6px; }
.code-block pre::-webkit-scrollbar-thumb { background: var(--border); }

.code-block.collapsed pre {
    max-height: 220px;
    overflow: hidden;
    position: relative;
    padding-bottom: 30px;
}
.code-block.collapsed pre::after {
    content: '';
    position: absolute;
    bottom: 0; left: 0; right: 0;
    height: 50px;
    background: linear-gradient(transparent, var(--code-bg));
    pointer-events: none;
}

.inline-code {
    background: var(--code-bg);
    padding: 1px 5px;
    border-radius: 3px;
    font-family: 'SFMono-Regular', Consolas, monospace;
    font-size: 12px;
    color: #ffa657;
    border: 1px solid var(--border);
}
[data-theme="light"] .inline-code { color: #cf222e; }

/* ========== Attachments ========== */
.attachments { margin-top: 6px; display: flex; flex-wrap: wrap; gap: 6px; }
.att {
    display: inline-flex; align-items: center; gap: 6px;
    background: var(--bg-3);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 5px 10px;
    text-decoration: none;
    color: var(--text);
    font-size: 12px;
}
.att:hover { background: var(--bg-hover); }
.att .att-icon { font-size: 14px; }
.att .att-size { color: var(--text-dim); font-size: 11px; }
.att-img-thumb {
    max-width: 200px; max-height: 200px;
    border-radius: 6px; border: 1px solid var(--border);
    cursor: pointer; display: block;
}

/* ========== Reply preview / pending attachments ========== */
.reply-preview {
    background: var(--bg-3);
    border-top: 1px solid var(--border);
    padding: 8px 12px;
    display: none;
    align-items: center; gap: 8px;
    font-size: 12px;
}
.reply-preview.active { display: flex; }
.reply-preview .reply-text {
    flex: 1; color: var(--text-dim);
    overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.reply-preview .reply-text strong { color: var(--accent); }
.reply-preview .close-reply {
    background: transparent; border: none;
    color: var(--text-dim); cursor: pointer; font-size: 16px;
}

.pending-attachments {
    background: var(--bg-3);
    border-top: 1px solid var(--border);
    padding: 8px 12px;
    display: none;
    flex-wrap: wrap; gap: 6px;
}
.pending-attachments.active { display: flex; }
.pending-att {
    background: var(--bg-2);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 4px 8px;
    display: flex; align-items: center; gap: 6px;
    font-size: 12px;
}
.pending-att .remove {
    background: transparent; border: none;
    color: var(--danger); cursor: pointer; font-size: 14px;
}

/* ========== Input area ========== */
.input-area {
    border-top: 1px solid var(--border);
    background: var(--bg-2);
    padding: 10px 12px;
    display: flex; gap: 8px; align-items: flex-end;
}
.input-area textarea {
    flex: 1;
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 8px 10px;
    border-radius: 6px;
    resize: none;
    font-family: inherit;
    font-size: 14px;
    min-height: 38px;
    max-height: 200px;
    line-height: 1.5;
    outline: none;
}
.input-area textarea:focus { border-color: var(--accent); }
.input-area .file-btn {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    width: 38px; height: 38px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 18px;
    display: inline-flex; align-items: center; justify-content: center;
}
.input-area .file-btn:hover { background: var(--bg-hover); }

/* ========== Sidebar ========== */
.sidebar {
    background: var(--bg-2);
    overflow-y: auto;
    padding: 12px;
}
.sidebar::-webkit-scrollbar { width: 6px; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); }

.sidebar-filter {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 8px;
    margin-bottom: 12px;
}
.sidebar-filter .label {
    font-size: 11px;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 6px;
}
.sidebar-filter .chips {
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
}

.side-section {
    margin-bottom: 12px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
}
.side-section h3 {
    padding: 8px 12px;
    background: var(--bg-3);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-dim);
    cursor: pointer;
    display: flex; justify-content: space-between; align-items: center;
    user-select: none;
    font-weight: 600;
}
.side-section h3:hover { background: var(--bg-hover); }
.side-section h3 .left { display: flex; align-items: center; gap: 6px; }
.side-section h3 .count {
    background: var(--accent);
    color: white;
    padding: 1px 6px;
    border-radius: 10px;
    font-size: 10px;
}
.side-section h3 .arrow { transition: transform 0.2s; font-size: 10px; }
.side-section.collapsed h3 .arrow { transform: rotate(-90deg); }
.side-section .toolbar {
    display: flex;
    gap: 4px;
    padding: 6px 8px;
    background: var(--bg-2);
    border-bottom: 1px solid var(--border);
    font-size: 11px;
}
.side-section.collapsed .toolbar,
.side-section.collapsed .body { display: none; }
.side-section .toolbar button {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 3px 7px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 11px;
    font-family: inherit;
}
.side-section .toolbar button:hover { background: var(--bg-hover); }
.side-section .toolbar button.active { background: var(--accent); border-color: var(--accent); color: white; }
.side-section .toolbar .spacer { flex: 1; }

.side-section .body { max-height: 280px; overflow-y: auto; }
.side-section .body::-webkit-scrollbar { width: 4px; }
.side-section .body::-webkit-scrollbar-thumb { background: var(--border); }

.side-item {
    padding: 6px 10px;
    border-bottom: 1px solid var(--border);
    font-size: 12px;
    display: flex; align-items: center; gap: 6px;
    cursor: pointer;
}
.side-item:last-child { border-bottom: none; }
.side-item:hover { background: var(--bg-3); }
.side-item input[type="checkbox"] {
    accent-color: var(--accent);
    cursor: pointer;
    flex-shrink: 0;
}
.side-item.select-mode { padding-left: 6px; }
.side-item a {
    color: var(--text);
    text-decoration: none;
    flex: 1;
    overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.side-item a:hover { color: var(--accent); }
.side-item .icon { flex-shrink: 0; }
.side-item .att-size { color: var(--text-dim); font-size: 11px; }
.side-item.empty { color: var(--text-dim); cursor: default; padding: 10px; text-align: center; font-style: italic; }
.side-item.empty:hover { background: transparent; }

.side-img-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 4px;
    padding: 6px;
    position: relative;
}
.side-img-grid .img-cell { position: relative; }
.side-img-grid img {
    width: 100%;
    aspect-ratio: 1;
    object-fit: cover;
    border-radius: 4px;
    cursor: pointer;
    border: 1px solid var(--border);
    display: block;
}
.side-img-grid input[type="checkbox"] {
    position: absolute;
    top: 4px;
    left: 4px;
    accent-color: var(--accent);
    display: none;
    z-index: 2;
    background: white;
}
.side-section.select-mode .side-img-grid input[type="checkbox"] { display: block; }

/* Code item trong sidebar — hiển thị nhiều dòng meta */
.side-item.code-item {
    align-items: flex-start;
    padding: 8px 10px;
}
.side-item.code-item .code-meta {
    flex: 1;
    min-width: 0;
    display: flex;
    flex-direction: column;
    gap: 2px;
}
.side-item.code-item .code-lang {
    font-weight: 600;
    color: var(--accent);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    display: flex;
    align-items: center;
    gap: 6px;
}
.side-item.code-item .code-lines {
    color: var(--text-dim);
    font-weight: 400;
    text-transform: none;
    font-size: 11px;
    letter-spacing: 0;
}
.side-item.code-item .code-preview {
    font-family: 'SFMono-Regular', Consolas, monospace;
    font-size: 11px;
    color: var(--text-dim);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* Tag thống kê ngôn ngữ */
.lang-stats {
    padding: 6px 8px;
    background: var(--bg-2);
    border-bottom: 1px solid var(--border);
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
}
.lang-tag {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 2px 8px;
    border-radius: 10px;
    font-size: 10px;
    text-transform: uppercase;
    letter-spacing: 0.3px;
    font-weight: 600;
}

/* ========== Lightbox ========== */
.lightbox {
    position: fixed; inset: 0;
    background: rgba(0,0,0,0.92);
    z-index: 1000;
    display: none;
    align-items: center; justify-content: center;
    padding: 20px;
    cursor: zoom-out;
}
.lightbox.active { display: flex; }
.lightbox img {
    max-width: 95%; max-height: 95%;
    object-fit: contain;
    border-radius: 4px;
}

/* ========== Toast ========== */
.toast-container {
    position: fixed; top: 16px; right: 16px;
    z-index: 2000;
    display: flex; flex-direction: column; gap: 8px;
    pointer-events: none;
}
.toast {
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    border-radius: 6px;
    padding: 10px 14px;
    font-size: 13px;
    box-shadow: 0 4px 12px var(--shadow);
    animation: slideIn 0.25s ease;
    pointer-events: auto;
    max-width: 360px;
}
.toast.success { border-left: 3px solid var(--success); }
.toast.error   { border-left: 3px solid var(--danger); }
.toast.info    { border-left: 3px solid var(--accent); }
@keyframes slideIn { from { transform: translateX(100%); opacity: 0; } to { transform: translateX(0); opacity: 1; } }

/* ========== Modal ========== */
.modal-overlay {
    position: fixed; inset: 0;
    background: rgba(0,0,0,0.55);
    z-index: 1500;
    display: none;
    align-items: center; justify-content: center;
    padding: 20px;
}
.modal-overlay.active { display: flex; }
.modal {
    background: var(--bg-2);
    border: 1px solid var(--border);
    border-radius: 12px;
    width: 100%;
    max-width: 480px;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 12px 32px var(--shadow);
}
.modal-head {
    padding: 14px 18px;
    border-bottom: 1px solid var(--border);
    display: flex; align-items: center; justify-content: space-between;
}
.modal-head h2 { font-size: 16px; }
.modal-head .close {
    background: transparent; border: none; color: var(--text-dim);
    cursor: pointer; font-size: 22px; line-height: 1;
}
.modal-body { padding: 18px; }
.modal-body label {
    display: block;
    margin-bottom: 12px;
}
.modal-body label > span {
    display: block;
    font-size: 12px;
    color: var(--text-dim);
    margin-bottom: 4px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
.modal-body input[type="text"],
.modal-body input[type="password"] {
    width: 100%;
    padding: 8px 10px;
    background: var(--bg-3);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text);
    font-size: 14px;
    outline: none;
    font-family: inherit;
}
.modal-body input:focus { border-color: var(--accent); }
.modal-body .row {
    display: flex; gap: 10px; align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid var(--border);
}
.modal-body .row:last-child { border-bottom: none; }
.modal-body .row .label { flex: 1; }
.modal-body .row .label small { display: block; color: var(--text-dim); margin-top: 2px; }

.modal .qr-canvas {
    background: white;
    padding: 12px;
    border-radius: 8px;
    margin: 14px auto;
    display: block;
}

.modal .secret-box {
    font-family: 'SFMono-Regular', Consolas, monospace;
    background: var(--bg-3);
    padding: 8px 12px;
    border-radius: 6px;
    word-break: break-all;
    font-size: 13px;
    text-align: center;
    user-select: all;
}

.modal .recovery-codes {
    background: var(--bg-3);
    padding: 12px;
    border-radius: 6px;
    font-family: 'SFMono-Regular', Consolas, monospace;
    font-size: 13px;
    line-height: 1.8;
    columns: 2;
}

.theme-toggle-row {
    display: flex;
    gap: 6px;
}
.theme-toggle-row button {
    flex: 1;
    padding: 8px;
    background: var(--bg-3);
    border: 1px solid var(--border);
    color: var(--text);
    border-radius: 6px;
    cursor: pointer;
    font-family: inherit;
    font-size: 13px;
}
.theme-toggle-row button.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* ========== Mobile ========== */
.mobile-only { display: none; }
@media (max-width: 900px) {
    .app { grid-template-columns: 1fr; }
    .messages { padding: 12px 16px; }
    .input-area { padding: 10px 16px; }
    .reply-preview, .pending-attachments { padding-left: 16px; padding-right: 16px; }
    .sidebar {
        position: fixed; right: 0; top: 0; bottom: 0;
        width: 320px;
        transform: translateX(100%);
        transition: transform 0.25s;
        z-index: 100;
        box-shadow: -4px 0 16px var(--shadow);
    }
    .sidebar.open { transform: translateX(0); }
    .msg { max-width: 95%; }
    .mobile-only { display: inline-flex; }
}