feat: add breadcrumb navigation and refactor SPA view management

- Add breadcrumb navigation with folder hierarchy display
- Create setCurrentSection() helper to centralize view state management
- Derive nav item section dynamically from DOM data-i18n attribute
- Remove remnant /shared page and consolidate to SPA sharedView
- Add search input to sharedView for client-side filtering
- Fix 'Go to Files' button to use switchToFilesView()

static/css/components/breadcrumb.css

@@ -38,3 +38,20 @@
 	font-size: 12px;
 	user-select: none;
 }
+
+.breadcrumb-home {
+	display: inline-flex;
+	align-items: center;
+	justify-content: center;
+	width: 24px;
+	height: 24px;
+	border-radius: 4px;
+}
+
+.breadcrumb-home i {
+	font-size: 12px;
+}
+
+.breadcrumb-home.breadcrumb-link:hover {
+	background: rgba(255, 94, 58, 0.1);
+}

static/css/themes/dark.css

@@ -97,6 +97,15 @@
     color: #64748b;
 }
 
+[data-theme="dark"] .breadcrumb-home {
+    color: #94a3b8;
+}
+
+[data-theme="dark"] .breadcrumb-home.breadcrumb-link:hover {
+    color: #ff5e3a;
+    background: rgba(255, 94, 58, 0.15);
+}
+
 [data-theme="dark"] .btn-secondary {
     background-color: #1e293b;
     color: #cbd5e1;