chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/tests/core/test_mapping_service.py

@@ -4,21 +4,21 @@
 # @LAYER:     Domain
 # @RELATION:  VERIFIES ->[src.core.mapping_service.IdMappingService]
 #
+import sys
+from datetime import UTC, datetime
+from pathlib import Path
+
 import pytest
-from datetime import datetime, timezone
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
-import sys
-import os
-from pathlib import Path
 
 # Add backend directory to sys.path so 'src' can be resolved
 backend_dir = str(Path(__file__).parent.parent.parent.resolve())
 if backend_dir not in sys.path:
     sys.path.insert(0, backend_dir)
 
-from src.models.mapping import Base, ResourceMapping, ResourceType
 from src.core.mapping_service import IdMappingService
+from src.models.mapping import Base, ResourceMapping, ResourceType
 
 
 @pytest.fixture
@@ -80,7 +80,7 @@ def test_get_remote_id_returns_integer(db_session):
         uuid="uuid-1",
         remote_integer_id="99",
         resource_name="Test DS",
-        last_synced_at=datetime.now(timezone.utc),
+        last_synced_at=datetime.now(UTC),
     )
     db_session.add(mapping)
     db_session.commit()