refactor: modernize code quality tooling with Ruff

- Replace black, isort, and flake8 with Ruff (all-in-one linter and formatter)
- Add comprehensive pyproject.toml configuration
- Simplify Makefile code quality targets
- Configure exclusions for venv/.venv in pyproject.toml
- Auto-fix 1,359 linting issues across codebase

Benefits:
- Much faster builds (Ruff is written in Rust)
- Single tool replaces multiple tools
- More comprehensive rule set (UP, B, C4, SIM, PIE, RET, Q)
- All configuration centralized in pyproject.toml
- Better import sorting and formatting consistency

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/services/product_service.py

@@ -9,13 +9,15 @@ This module provides:
 """
 
 import logging
-from datetime import datetime, timezone
-from typing import List, Optional, Tuple
+from datetime import UTC, datetime
 
 from sqlalchemy.orm import Session
 
-from app.exceptions import (ProductAlreadyExistsException,
-                            ProductNotFoundException, ValidationException)
+from app.exceptions import (
+    ProductAlreadyExistsException,
+    ProductNotFoundException,
+    ValidationException,
+)
 from models.database.marketplace_product import MarketplaceProduct
 from models.database.product import Product
 from models.schema.product import ProductCreate, ProductUpdate
@@ -106,7 +108,7 @@ class ProductService:
 
             if existing:
                 raise ProductAlreadyExistsException(
-                    f"Product already exists in catalog"
+                    "Product already exists in catalog"
                 )
 
             # Create product
@@ -167,7 +169,7 @@ class ProductService:
             for key, value in update_data.items():
                 setattr(product, key, value)
 
-            product.updated_at = datetime.now(timezone.utc)
+            product.updated_at = datetime.now(UTC)
             db.commit()
             db.refresh(product)
 
@@ -216,9 +218,9 @@ class ProductService:
         vendor_id: int,
         skip: int = 0,
         limit: int = 100,
-        is_active: Optional[bool] = None,
-        is_featured: Optional[bool] = None,
-    ) -> Tuple[List[Product], int]:
+        is_active: bool | None = None,
+        is_featured: bool | None = None,
+    ) -> tuple[list[Product], int]:
         """
         Get products in vendor catalog with filtering.