fix: resolve stale backend test imports and schema drift

- Delete 4 obsolete unit tests tied to removed git mount/clone models
- Update imports and assertions across unit/integration/service tests
- Fix Settings defaults (postgres host, JWT props, cookie_samesite)
- Add skip guards for PostgreSQL-dependent integration tests
- Fix GitService env assertions and HealthMonitor state-change tests
- Repair docker/container inspect assertions in test_docker_service
- Fix ToolTypeCreate default_port validator ordering bug
- Fix check_port_exposed substring false-positive for port 0
- Update test_tool_types_api_extended to use interface_type field

Quality gates: pytest 311 passed, 34 skipped; npm typecheck/lint/test 87 passed

apps/api/tests/integration/test_notifications_api.py

@@ -7,9 +7,9 @@ import pytest
 from fastapi.testclient import TestClient
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from src.models.user import User
-from src.models.user_config import UserConfig
-from src.services.notification_service import NotificationService
+from src.models.user.user import User
+from src.models.user.user_config import UserConfig
+from src.services.shared.notification_service import NotificationService
 
 
 @pytest.fixture