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/exceptions/product.py

@@ -4,12 +4,9 @@ Product (vendor catalog) specific exceptions.
 """
 
 from typing import Optional
-from .base import (
-    ResourceNotFoundException,
-    ConflictException,
-    ValidationException,
-    BusinessLogicException
-)
+
+from .base import (BusinessLogicException, ConflictException,
+                   ResourceNotFoundException, ValidationException)
 
 
 class ProductNotFoundException(ResourceNotFoundException):