feat: implement full breadcrumb path navigation in Files tab

- Add breadcrumbPath array to app state for tracking folder hierarchy
- Rewrite updateBreadcrumb() to render full path: Home > folder > subfolder
- Each breadcrumb segment is clickable to navigate back to that level
- Current folder shown in bold (non-clickable), parent folders as links
- Reset breadcrumb path on tab switch, home navigation, and initial load
- Update navigateFolder/selectFolder to push to breadcrumb path
- Enhanced breadcrumb CSS with hover effects and dark mode support

static/css/components/multiSelect.css

@@ -0,0 +1,153 @@
+/* Multi-Select – checkboxes & batch action bar */
+.list-header-checkbox,
+.list-item-checkbox {
+	display: flex;
+	align-items: center;
+	justify-content: center;
+}
+
+.list-header-checkbox input[type="checkbox"],
+.list-item-checkbox input[type="checkbox"] {
+	width: 17px;
+	height: 17px;
+	cursor: pointer;
+	accent-color: #ff5e3a;
+	border-radius: 4px;
+}
+
+.list-header.selection-mode {
+	grid-template-columns: 36px 1fr;
+	background-color: #1e293b;
+	color: #fff;
+	border-bottom-color: #334155;
+}
+
+.list-header.selection-mode .list-header-checkbox input[type="checkbox"] {
+	accent-color: #ff5e3a;
+}
+
+.batch-selection-info {
+	display: flex;
+	align-items: center;
+	justify-content: space-between;
+	gap: 16px;
+	min-width: 0;
+}
+
+.batch-action-bar {
+	display: flex;
+	align-items: center;
+	justify-content: space-between;
+	background: #1e293b;
+	color: #fff;
+	padding: 10px 20px;
+	border-radius: 12px;
+	margin: 0 0 12px;
+	opacity: 0;
+	max-height: 0;
+	overflow: hidden;
+	transform: translateY(-8px);
+	transition: opacity 0.2s, max-height 0.25s, transform 0.2s, margin 0.2s, padding 0.2s;
+	pointer-events: none;
+}
+
+.batch-action-bar.visible {
+	opacity: 1;
+	max-height: 60px;
+	transform: translateY(0);
+	pointer-events: auto;
+	padding: 10px 20px;
+	margin: 0 0 12px;
+}
+
+.batch-bar-left {
+	display: flex;
+	align-items: center;
+	gap: 12px;
+}
+
+.batch-bar-close {
+	background: none;
+	border: none;
+	color: rgba(255,255,255,0.7);
+	cursor: pointer;
+	font-size: 14px;
+	padding: 4px 6px;
+	border-radius: 6px;
+	transition: background 0.15s, color 0.15s;
+}
+
+.batch-bar-close:hover {
+	background: rgba(255,255,255,0.1);
+	color: #fff;
+}
+
+.batch-bar-count {
+	font-size: 14px;
+	font-weight: 600;
+	white-space: nowrap;
+}
+
+.batch-bar-actions {
+	display: flex;
+	align-items: center;
+	gap: 6px;
+}
+
+.batch-btn {
+	display: inline-flex;
+	align-items: center;
+	gap: 6px;
+	padding: 7px 14px;
+	border: none;
+	border-radius: 8px;
+	background: rgba(255,255,255,0.1);
+	color: #fff;
+	font-size: 13px;
+	font-weight: 500;
+	cursor: pointer;
+	transition: background 0.15s;
+	white-space: nowrap;
+}
+
+.batch-btn:hover {
+	background: rgba(255,255,255,0.2);
+}
+
+.batch-btn-danger {
+	background: rgba(239,68,68,0.25);
+	color: #fca5a5;
+}
+
+.batch-btn-danger:hover {
+	background: rgba(239,68,68,0.4);
+	color: #fff;
+}
+
+@media (max-width: 640px) {
+	.batch-btn span {
+		display: none;
+	}
+
+	.batch-btn {
+		padding: 7px 10px;
+	}
+}
+
+[data-theme="dark"] .list-header-checkbox input,
+[data-theme="dark"] .list-item-checkbox input,
+[data-theme="dark"] .file-card-checkbox input {
+	accent-color: #ff5e3a;
+}
+
+[data-theme="dark"] .batch-action-bar {
+	background-color: #1e293b;
+	border-color: #334155;
+	color: #e2e8f0;
+}
+
+[data-theme="dark"] .list-header.selection-mode {
+	background-color: #0f172a;
+	border-bottom-color: #334155;
+	color: #e2e8f0;
+}