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/schema/product.py

@@ -1,14 +1,20 @@
 # models/schema/product.py
 from datetime import datetime
 from typing import List, Optional
+
 from pydantic import BaseModel, ConfigDict, Field
-from models.schema.marketplace_product import MarketplaceProductResponse
+
 from models.schema.inventory import InventoryLocationResponse
+from models.schema.marketplace_product import MarketplaceProductResponse
 
 
 class ProductCreate(BaseModel):
-    marketplace_product_id: int = Field(..., description="MarketplaceProduct ID to add to vendor catalog")
-    product_id: Optional[str] = Field(None, description="Vendor's internal SKU/product ID")
+    marketplace_product_id: int = Field(
+        ..., description="MarketplaceProduct ID to add to vendor catalog"
+    )
+    product_id: Optional[str] = Field(
+        None, description="Vendor's internal SKU/product ID"
+    )
     price: Optional[float] = Field(None, ge=0)
     sale_price: Optional[float] = Field(None, ge=0)
     currency: Optional[str] = None
@@ -59,6 +65,7 @@ class ProductResponse(BaseModel):
 
 class ProductDetailResponse(ProductResponse):
     """Product with full inventory details."""
+
     inventory_locations: List[InventoryLocationResponse] = []