Refactor(backend): improve formatting in services, repositories & tests

- Consistently format multi-line function headers, exception handling, and repository method calls for readability.
- Reorganize misplaced imports across modules (e.g., services & tests) into proper sorted order.
- Adjust indentation, line breaks, and spacing inconsistencies in tests and migration files.
- Cleanup unnecessary trailing newlines and reorganize `__all__` declarations for consistency.

backend/app/repositories/__init__.py

@@ -18,22 +18,22 @@ from app.repositories.session import SessionRepository, session_repo
 from app.repositories.user import UserRepository, user_repo
 
 __all__ = [
-    "UserRepository",
-    "user_repo",
-    "OrganizationRepository",
-    "organization_repo",
-    "SessionRepository",
-    "session_repo",
     "OAuthAccountRepository",
-    "oauth_account_repo",
     "OAuthAuthorizationCodeRepository",
-    "oauth_authorization_code_repo",
     "OAuthClientRepository",
-    "oauth_client_repo",
     "OAuthConsentRepository",
-    "oauth_consent_repo",
     "OAuthProviderTokenRepository",
-    "oauth_provider_token_repo",
     "OAuthStateRepository",
+    "OrganizationRepository",
+    "SessionRepository",
+    "UserRepository",
+    "oauth_account_repo",
+    "oauth_authorization_code_repo",
+    "oauth_client_repo",
+    "oauth_consent_repo",
+    "oauth_provider_token_repo",
     "oauth_state_repo",
+    "organization_repo",
+    "session_repo",
+    "user_repo",
 ]