ci: add ruff linting and mypy type checking

Add ruff and mypy to dev dependencies with configuration in pyproject.toml.
Add a lint CI job that runs ruff check, ruff format --check, and mypy.
Auto-fix import sorting and formatting across the codebase. Exclude
alembic/versions from linting (auto-generated migrations). Ignore B008
(FastAPI Depends pattern) and RUF001 (unicode in user-facing strings).

21 ruff lint errors and 50 mypy errors remain for manual review.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/integration/helpers.py

@@ -6,6 +6,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.auth.security import PasswordService
 
+
 def login_user(client: TestClient, *, email: str, password: str) -> None:
     bootstrap_response = client.get("/api/v1/auth/csrf")
     assert bootstrap_response.status_code == 200