fix(frontend): add data parameter support to apiDelete

- Add optional data parameter to apiDelete() with generic type safety
- Enables DELETE requests with request bodies (needed for folder deletion)
- 100% backward compatible (optional parameter)
- Supports type-safe request body passing

Part of: Issue 1

web/src/api.ts

@@ -34,12 +34,14 @@ async function apiPut(url: string, data?: unknown): Promise<Response> {
     });
 }
 
-async function apiDelete(url: string): Promise<Response> {
+async function apiDelete<T extends object>(url: string, data?: T): Promise<Response> {
     return fetch(`/api${url}`, {
         method: 'DELETE',
         headers: {
-            'Authorization': getAuthHeader()
-        }
+            'Authorization': getAuthHeader(),
+            'Content-Type': 'application/json'
+        },
+        body: data ? JSON.stringify(data) : undefined
     });
 }