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/dashboard.py

@@ -5,6 +5,7 @@ Admin dashboard and statistics endpoints.
 
 import logging
 from typing import List
+
 from fastapi import APIRouter, Depends
 from sqlalchemy.orm import Session
 
@@ -87,4 +88,4 @@ def get_platform_statistics(
         "products": stats_service.get_product_statistics(db),
         "orders": stats_service.get_order_statistics(db),
         "imports": stats_service.get_import_statistics(db),
-    }
+    }