fix: task 1.5 poster check + fix stuck tests

- Fix structlog format string in folder_scan_service (%(key)d -> kwargs)
- Add nfo_download_poster setting check before poster download
- Create missing NFO fixture files (tvshow.nfo.bad/good) for repair tests
- Fix test_context_used_in_logging to check all call args not format string
- Fix test_system_settings_integration isolation via reset_all_scans

tests/unit/test_system_settings_service.py

@@ -10,8 +10,12 @@ async def test_system_settings_integration():
     """Test SystemSettings service with actual database operations."""
     # Initialize database
     await init_db()
-    
-    # Test get_or_create (should create on first call)
+
+    # Reset all flags to a known-clean state before the test
+    async with get_db_session() as db:
+        await SystemSettingsService.reset_all_scans(db)
+
+    # Test get_or_create (should return record with all flags False after reset)
     async with get_db_session() as db:
         settings = await SystemSettingsService.get_or_create(db)
         assert settings is not None