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>

tests/integration/api/v1/test_vendor_endpoints.py

@@ -6,7 +6,6 @@ import pytest
 @pytest.mark.api
 @pytest.mark.vendors
 class TestVendorsAPI:
-
     def test_create_vendor_success(self, client, auth_headers):
         """Test creating a new vendor successfully"""
         vendor_data = {
@@ -91,7 +90,7 @@ class TestVendorsAPI:
 
         # Assuming max vendors is enforced at service level
         # This test validates the expected response structure
-        pass  # Implementation depends on your max_vendors business logic
+        # Implementation depends on your max_vendors business logic
 
     def test_get_vendors_success(self, client, auth_headers, test_vendor):
         """Test getting vendors list successfully"""