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/utils/csv_processor.py

@@ -195,7 +195,7 @@ class CSVProcessor:
         Args:
             url: URL to the CSV file
             marketplace: Name of the marketplace (e.g., 'Letzshop', 'Amazon')
-            vendor_name: Name of the vendor 
+            vendor_name: Name of the vendor
             batch_size: Number of rows to process in each batch
             db: Database session
 
@@ -267,7 +267,9 @@ class CSVProcessor:
 
                 # Validate required fields
                 if not product_data.get("marketplace_product_id"):
-                    logger.warning(f"Row {index}: Missing marketplace_product_id, skipping")
+                    logger.warning(
+                        f"Row {index}: Missing marketplace_product_id, skipping"
+                    )
                     errors += 1
                     continue
 
@@ -279,7 +281,10 @@ class CSVProcessor:
                 # Check if product exists
                 existing_product = (
                     db.query(MarketplaceProduct)
-                    .filter(MarketplaceProduct.marketplace_product_id == literal(product_data["marketplace_product_id"]))
+                    .filter(
+                        MarketplaceProduct.marketplace_product_id
+                        == literal(product_data["marketplace_product_id"])
+                    )
                     .first()
                 )