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>

models/database/marketplace_import_job.py

@@ -1,6 +1,7 @@
 from datetime import datetime, timezone
 
-from sqlalchemy import Column, DateTime, ForeignKey, Index, Integer, String, Text
+from sqlalchemy import (Column, DateTime, ForeignKey, Index, Integer, String,
+                        Text)
 from sqlalchemy.orm import relationship
 
 from app.core.database import Base