fix: resolve lint error and typecheck failures for MVP launch readiness

- Remove unused `registerUser` import in e2e/api/inquiries.spec.ts
- Add `override` modifier to class methods in query-provider.tsx

Co-Authored-By: Paperclip <noreply@paperclip.ing>

e2e/api/inquiries.spec.ts

@@ -1,4 +1,4 @@
-import { test, expect, createListing, registerUser } from '../fixtures';
+import { test, expect, createListing } from '../fixtures';
 
 test.describe('Inquiries API', () => {
   test('POST /inquiries — creates inquiry for a listing', async ({