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/stats.py

@@ -1,6 +1,6 @@
 import re
-from decimal import Decimal
 from datetime import datetime
+from decimal import Decimal
 from typing import List, Optional
 
 from pydantic import BaseModel, ConfigDict, EmailStr, Field, field_validator
@@ -22,10 +22,12 @@ class MarketplaceStatsResponse(BaseModel):
     unique_vendors: int
     unique_brands: int
 
+
 # ============================================================================
 # Customer Statistics
 # ============================================================================
 
+
 class CustomerStatsResponse(BaseModel):
     """Schema for customer statistics."""
 
@@ -42,8 +44,10 @@ class CustomerStatsResponse(BaseModel):
 # Order Statistics
 # ============================================================================
 
+
 class OrderStatsResponse(BaseModel):
     """Schema for order statistics."""
+
     total_orders: int
     pending_orders: int
     processing_orders: int
@@ -53,13 +57,16 @@ class OrderStatsResponse(BaseModel):
     total_revenue: Decimal
     average_order_value: Decimal
 
+
 # ============================================================================
 # Vendor Statistics
 # ============================================================================
 
+
 class VendorStatsResponse(BaseModel):
     """Vendor statistics response schema."""
+
     total: int = Field(..., description="Total number of vendors")
     verified: int = Field(..., description="Number of verified vendors")
     pending: int = Field(..., description="Number of pending verification vendors")
-    inactive: int = Field(..., description="Number of inactive vendors")
+    inactive: int = Field(..., description="Number of inactive vendors")