feat: improve transactions API pagination and search

- Update backend /transactions endpoint to use PaginatedResponse
- Change from limit/offset to page/per_page parameters for consistency
- Implement server-side pagination with proper metadata
- Add search debouncing to prevent excessive API calls (300ms delay)
- Add First/Last page buttons to pagination controls
- Fix pagination state reset when filters return 0 results
- Reset pagination to page 1 when filters are applied
- Add visual loading indicator during search debouncing
- Update frontend types and API client to handle new response structure
- Fix TypeScript errors and improve type safety

frontend/src/types/api.ts

@@ -124,6 +124,14 @@ export interface ApiResponse<T> {
   data: T;
   message?: string;
   success: boolean;
+  pagination?: {
+    total: number;
+    page: number;
+    per_page: number;
+    total_pages: number;
+    has_next: boolean;
+    has_prev: boolean;
+  };
 }
 
 export interface PaginatedResponse<T> {