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/tasks/background_tasks.py

@@ -3,9 +3,9 @@ import logging
 from datetime import datetime, timezone
 
 from app.core.database import SessionLocal
+from app.utils.csv_processor import CSVProcessor
 from models.database.marketplace_import_job import MarketplaceImportJob
 from models.database.vendor import Vendor
-from app.utils.csv_processor import CSVProcessor
 
 logger = logging.getLogger(__name__)
 
@@ -15,7 +15,7 @@ async def process_marketplace_import(
     url: str,
     marketplace: str,
     vendor_id: int,  # FIXED: Changed from vendor_name to vendor_id
-    batch_size: int = 1000
+    batch_size: int = 1000,
 ):
     """Background task to process marketplace CSV import."""
     db = SessionLocal()
@@ -59,7 +59,7 @@ async def process_marketplace_import(
             marketplace,
             vendor_id,  # FIXED: Pass vendor_id instead of vendor_name
             batch_size,
-            db
+            db,
         )
 
         # Update job with results