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/cart.py

@@ -5,21 +5,24 @@ Pydantic schemas for shopping cart operations.
 
 from datetime import datetime
 from typing import List, Optional
-from pydantic import BaseModel, Field, ConfigDict
 
+from pydantic import BaseModel, ConfigDict, Field
 
 # ============================================================================
 # Request Schemas
 # ============================================================================
 
+
 class AddToCartRequest(BaseModel):
     """Request model for adding items to cart."""
+
     product_id: int = Field(..., description="Product ID to add", gt=0)
     quantity: int = Field(1, ge=1, description="Quantity to add")
 
 
 class UpdateCartItemRequest(BaseModel):
     """Request model for updating cart item quantity."""
+
     quantity: int = Field(..., ge=1, description="New quantity (must be >= 1)")
 
 
@@ -27,23 +30,30 @@ class UpdateCartItemRequest(BaseModel):
 # Response Schemas
 # ============================================================================
 
+
 class CartItemResponse(BaseModel):
     """Response model for a single cart item."""
+
     model_config = ConfigDict(from_attributes=True)
 
     product_id: int = Field(..., description="Product ID")
     product_name: str = Field(..., description="Product name")
     quantity: int = Field(..., description="Quantity in cart")
     price: float = Field(..., description="Price per unit when added to cart")
-    line_total: float = Field(..., description="Total price for this line (price * quantity)")
+    line_total: float = Field(
+        ..., description="Total price for this line (price * quantity)"
+    )
     image_url: Optional[str] = Field(None, description="Product image URL")
 
 
 class CartResponse(BaseModel):
     """Response model for shopping cart."""
+
     vendor_id: int = Field(..., description="Vendor ID")
     session_id: str = Field(..., description="Shopping session ID")
-    items: List[CartItemResponse] = Field(default_factory=list, description="Cart items")
+    items: List[CartItemResponse] = Field(
+        default_factory=list, description="Cart items"
+    )
     subtotal: float = Field(..., description="Subtotal of all items")
     total: float = Field(..., description="Total amount (currently same as subtotal)")
     item_count: int = Field(..., description="Total number of items in cart")
@@ -63,18 +73,22 @@ class CartResponse(BaseModel):
             items=items,
             subtotal=cart_dict["subtotal"],
             total=cart_dict["total"],
-            item_count=len(items)
+            item_count=len(items),
         )
 
 
 class CartOperationResponse(BaseModel):
     """Response model for cart operations (add, update, remove)."""
+
     message: str = Field(..., description="Operation result message")
     product_id: int = Field(..., description="Product ID affected")
-    quantity: Optional[int] = Field(None, description="New quantity (for add/update operations)")
+    quantity: Optional[int] = Field(
+        None, description="New quantity (for add/update operations)"
+    )
 
 
 class ClearCartResponse(BaseModel):
     """Response model for clearing cart."""
+
     message: str = Field(..., description="Operation result message")
     items_removed: int = Field(..., description="Number of items removed from cart")