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/unit/services/test_auth_service.py

@@ -1,9 +1,11 @@
 # tests/test_auth_service.py
 import pytest
 
-from app.exceptions.auth import (InvalidCredentialsException,
-                                 UserAlreadyExistsException,
-                                 UserNotActiveException)
+from app.exceptions.auth import (
+    InvalidCredentialsException,
+    UserAlreadyExistsException,
+    UserNotActiveException,
+)
 from app.exceptions.base import ValidationException
 from app.services.auth_service import AuthService
 from models.schema.auth import UserLogin, UserRegister