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>

tests/fixtures/auth_fixtures.py

@@ -53,6 +53,7 @@ def test_admin(db, auth_manager):
     db.expunge(admin)
     return admin
 
+
 @pytest.fixture
 def another_admin(db, auth_manager):
     """Create another test admin user for testing admin-to-admin interactions"""
@@ -72,6 +73,7 @@ def another_admin(db, auth_manager):
     db.expunge(admin)
     return admin
 
+
 @pytest.fixture
 def other_user(db, auth_manager):
     """Create a different user for testing access controls"""

tests/fixtures/customer_fixtures.py

@@ -1,5 +1,6 @@
 # tests/fixtures/customer_fixtures.py
 import pytest
+
 from models.database.customer import Customer, CustomerAddress
 
 

tests/fixtures/marketplace_import_job_fixtures.py

@@ -1,5 +1,6 @@
 # tests/fixtures/marketplace_import_job_fixtures.py
 import pytest
+
 from models.database.marketplace_import_job import MarketplaceImportJob
 
 

tests/fixtures/marketplace_product_fixtures.py

@@ -117,7 +117,9 @@ def marketplace_product_factory():
 
 
 @pytest.fixture
-def test_marketplace_product_with_inventory(db, test_marketplace_product, test_inventory):
+def test_marketplace_product_with_inventory(
+    db, test_marketplace_product, test_inventory
+):
     """MarketplaceProduct with associated inventory record."""
     # Ensure they're linked by GTIN
     if test_marketplace_product.gtin != test_inventory.gtin:
@@ -126,6 +128,6 @@ def test_marketplace_product_with_inventory(db, test_marketplace_product, test_i
         db.refresh(test_inventory)
 
     return {
-        'marketplace_product': test_marketplace_product,
-        'inventory': test_inventory
+        "marketplace_product": test_marketplace_product,
+        "inventory": test_inventory,
     }

tests/fixtures/testing_fixtures.py

@@ -8,8 +8,9 @@ This module provides fixtures for:
 - Additional testing utilities
 """
 
-import pytest
 from unittest.mock import Mock
+
+import pytest
 from sqlalchemy.exc import SQLAlchemyError
 
 
@@ -26,7 +27,7 @@ def empty_db(db):
         "inventory",  # Fixed: singular not plural
         "products",  # Referenced by products
         "vendors",  # Has foreign key to users
-        "users"  # Base table
+        "users",  # Base table
     ]
 
     for table in tables_to_clear:

tests/fixtures/vendor_fixtures.py

@@ -1,10 +1,11 @@
 # tests/fixtures/vendor_fixtures.py
 import uuid
+
 import pytest
 
-from models.database.vendor import Vendor
-from models.database.product import Product
 from models.database.inventory import Inventory
+from models.database.product import Product
+from models.database.vendor import Vendor
 
 
 @pytest.fixture
@@ -185,6 +186,7 @@ def multiple_inventory_entries(db, multiple_products, test_vendor):
 
 def create_unique_vendor_factory():
     """Factory function to create unique vendors in tests"""
+
     def _create_vendor(db, owner_user_id, **kwargs):
         unique_id = str(uuid.uuid4())[:8]
         defaults = {