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/api/v1/vendor/inventory.py

@@ -1,6 +1,5 @@
 # app/api/v1/vendor/inventory.py
 import logging
-from typing import List, Optional
 
 from fastapi import APIRouter, Depends, Query
 from sqlalchemy.orm import Session
@@ -11,10 +10,15 @@ from app.services.inventory_service import inventory_service
 from middleware.vendor_context import require_vendor_context
 from models.database.user import User
 from models.database.vendor import Vendor
-from models.schema.inventory import (InventoryAdjust, InventoryCreate,
-                                     InventoryListResponse, InventoryReserve,
-                                     InventoryResponse, InventoryUpdate,
-                                     ProductInventorySummary)
+from models.schema.inventory import (
+    InventoryAdjust,
+    InventoryCreate,
+    InventoryListResponse,
+    InventoryReserve,
+    InventoryResponse,
+    InventoryUpdate,
+    ProductInventorySummary,
+)
 
 router = APIRouter()
 logger = logging.getLogger(__name__)
@@ -90,8 +94,8 @@ def get_product_inventory(
 def get_vendor_inventory(
     skip: int = Query(0, ge=0),
     limit: int = Query(100, ge=1, le=1000),
-    location: Optional[str] = Query(None),
-    low_stock: Optional[int] = Query(None, ge=0),
+    location: str | None = Query(None),
+    low_stock: int | None = Query(None, ge=0),
     vendor: Vendor = Depends(require_vendor_context()),
     current_user: User = Depends(get_current_vendor_api),
     db: Session = Depends(get_db),