refactor(tests): replace crud references with repo across repository test files

- Updated import statements and test logic to align with `repositories` naming changes.
- Adjusted documentation and test names for consistency with the updated naming convention.
- Improved test descriptions to reflect the repository-based structure.

backend/app/repositories/oauth_account.py

@@ -1,5 +1,5 @@
 # app/repositories/oauth_account.py
-"""Repository for OAuthAccount model async CRUD operations."""
+"""Repository for OAuthAccount model async database operations."""
 
 import logging
 from datetime import datetime