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/unit/test_ingestion_arxiv_rate_limit.py

@@ -31,6 +31,7 @@ async def test_discover_identifiers_for_enrichment_disables_arxiv_on_rate_limit(
         _raise_rate_limit,
     )
     monkeypatch.setattr(identifier_service, "sync_identifiers_for_publication_fields", _sync_fields)
+
     async def _publish_noop(*args, **kwargs) -> None:
         _ = (args, kwargs)