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_auth_endpoints.py

@@ -1,5 +1,5 @@
 # tests/integration/api/v1/test_auth_endpoints.py
-from datetime import datetime, timedelta, timezone
+from datetime import UTC, datetime, timedelta
 
 import pytest
 from jose import jwt
@@ -196,8 +196,8 @@ class TestAuthenticationAPI:
             "username": test_user.username,
             "email": test_user.email,
             "role": test_user.role,
-            "exp": datetime.now(timezone.utc) - timedelta(hours=1),
-            "iat": datetime.now(timezone.utc) - timedelta(hours=2),
+            "exp": datetime.now(UTC) - timedelta(hours=1),
+            "iat": datetime.now(UTC) - timedelta(hours=2),
         }
 
         expired_token = jwt.encode(