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/tests/services/test_organization_service.py

@@ -4,12 +4,11 @@
 import uuid
 
 import pytest
-import pytest_asyncio
 
 from app.core.exceptions import NotFoundError
 from app.models.user_organization import OrganizationRole
 from app.schemas.organizations import OrganizationCreate, OrganizationUpdate
-from app.services.organization_service import OrganizationService, organization_service
+from app.services.organization_service import organization_service
 
 
 def _make_org_create(name=None, slug=None) -> OrganizationCreate:
@@ -50,9 +49,7 @@ class TestGetOrganization:
         _test_engine, AsyncTestingSessionLocal = async_test_db
         async with AsyncTestingSessionLocal() as session:
             with pytest.raises(NotFoundError):
-                await organization_service.get_organization(
-                    session, str(uuid.uuid4())
-                )
+                await organization_service.get_organization(session, str(uuid.uuid4()))
 
 
 class TestCreateOrganization:

backend/tests/services/test_session_service.py

@@ -5,10 +5,9 @@ import uuid
 from datetime import UTC, datetime, timedelta
 
 import pytest
-import pytest_asyncio
 
 from app.schemas.sessions import SessionCreate
-from app.services.session_service import SessionService, session_service
+from app.services.session_service import session_service
 
 
 def _make_session_create(user_id, jti=None) -> SessionCreate:

backend/tests/services/test_user_service.py

@@ -4,13 +4,12 @@
 import uuid
 
 import pytest
-import pytest_asyncio
 from sqlalchemy import select
 
 from app.core.exceptions import NotFoundError
 from app.models.user import User
 from app.schemas.users import UserCreate, UserUpdate
-from app.services.user_service import UserService, user_service
+from app.services.user_service import user_service
 
 
 class TestGetUser: