feat: implement QuestionBank CRUD with pagination and template query

- Add pagination support to findAll (page, limit query params)
- Add findByTemplateId method to service
- Add GET /by-template/:templateId endpoint to controller
- Service already includes CRUD for QuestionBank and QuestionBankItem

server/src/migrations/restore-timestamps.sql

@@ -0,0 +1,8 @@
+-- restore-timestamps.sql
+-- Restore created_at and updated_at columns to user_settings table.
+
+ALTER TABLE user_settings ADD COLUMN created_at datetime;
+ALTER TABLE user_settings ADD COLUMN updated_at datetime;
+
+UPDATE user_settings SET created_at = datetime('now') WHERE created_at IS NULL;
+UPDATE user_settings SET updated_at = datetime('now') WHERE updated_at IS NULL;