fix: folder trash/delete operations & frontend refactoring

- Fix recursive CTE: add missing RECURSIVE keyword in move_to_trash and restore_from_trash SQL queries (relation 'descendants' does not exist)
- Fix folder deletion: delete descendant files before folder to avoid 'duplicate key violates unique constraint idx_files_unique_name_at_root'
- Simplify trash model: only mark the folder as trashed, not child files (implicit trash via parent)
- Update trash_items view: filter to show only top-level trashed items
- Update schema.sql: change files.folder_id FK from ON DELETE SET NULL to ON DELETE CASCADE
- Fix trash view icons: folders and files now show correct visual icons (folder-icon, pdf-icon, etc.) in trash view
- Frontend refactoring: extract inline CSS/JS from admin.html and profile.html into dedicated external files
- Frontend cleanup: replace all inline style attributes with CSS classes
- Frontend cleanup: replace style.display JS
- Fix recursive CTE: add missing RECURSIVE keyword in move_to_trash and restore_from_trash SQL queries (relation 'descendants' d

static/js/app/state.js

@@ -0,0 +1,26 @@
+/**
+ * OxiCloud - App state container
+ * Centralized mutable state for app and cached DOM references.
+ */
+
+window.app = {
+    currentView: 'grid',
+    currentPath: '',
+    currentFolder: null,
+    contextMenuTargetFolder: null,
+    contextMenuTargetFile: null,
+    selectedTargetFolderId: '',
+    moveDialogMode: 'file',
+    isTrashView: false,
+    isSharedView: false,
+    isFavoritesView: false,
+    isRecentView: false,
+    currentSection: 'files',
+    isSearchMode: false,
+    shareDialogItem: null,
+    shareDialogItemType: null,
+    notificationShareUrl: null
+};
+
+window.appElements = {
+};