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/main.css

@@ -0,0 +1,29 @@
+/* Base */
+@import url("./base/variables.css");
+@import url("./base/reset.css");
+@import url("./base/forms.css");
+
+/* Layout */
+@import url("./layout/sidebar.css");
+@import url("./layout/topbar.css");
+@import url("./layout/content.css");
+
+/* Components */
+@import url("./components/breadcrumb.css");
+@import url("./components/buttons.css");
+@import url("./components/cards.css");
+@import url("./components/fileList.css");
+@import url("./components/contextMenu.css");
+@import url("./components/dialogs.css");
+@import url("./components/modals.css");
+@import url("./components/shareDialog.css");
+@import url("./components/uploadDropdown.css");
+@import url("./components/notifications.css");
+@import url("./components/userMenu.css");
+@import url("./components/languageSelector.css");
+@import url("./components/multiSelect.css");
+@import url("./components/spinner.css");
+@import url("./components/search.css");
+
+/* Theme */
+@import url("./themes/dark.css");