style: apply black and isort formatting across entire codebase

- Standardize quote style (single to double quotes)
- Reorder and group imports alphabetically
- Fix line breaks and indentation for consistency
- Apply PEP 8 formatting standards

Also updated Makefile to exclude both venv and .venv from code quality checks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/api/v1/admin/marketplace.py

@@ -13,8 +13,8 @@ from app.api.deps import get_current_admin_api
 from app.core.database import get_db
 from app.services.admin_service import admin_service
 from app.services.stats_service import stats_service
-from models.schema.marketplace_import_job import MarketplaceImportJobResponse
 from models.database.user import User
+from models.schema.marketplace_import_job import MarketplaceImportJobResponse
 
 router = APIRouter(prefix="/marketplace-import-jobs")
 logger = logging.getLogger(__name__)