Refactor processing logic and enhance error handling

- Cleaned up code in processing.py by removing inline semicolons and improving readability.
- Updated upsert_file_relation calls to ensure consistent handling of file relations.
- Enhanced query_file_relations in db_schema.py to support filtering by file existence.
- Improved API error handling in index.ts with user-friendly messages for 401 and 403 errors.
- Added online/offline status tracking in Layout.vue.
- Implemented debounced search functionality across multiple views to optimize performance.
- Introduced loading skeletons in Dashboard.vue for better user experience during data fetching.
- Enhanced file preview cleanup logic in Images.vue, Orders.vue, and Tables.vue to prevent memory leaks.
- Updated global styles to include new loading and notification animations.

web/frontend/src/router/index.ts

@@ -83,4 +83,14 @@ router.beforeEach((to, from, next) => {
   }
 })
 
+// Track route loading state for page transitions
+let routeLoadingTimer: ReturnType<typeof setTimeout> | null = null
+
+router.afterEach(() => {
+  if (routeLoadingTimer) clearTimeout(routeLoadingTimer)
+  routeLoadingTimer = setTimeout(() => {
+    routeLoadingTimer = null
+  }, 300)
+})
+
 export default router