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>

app/services/domains/arxiv/application.py

@@ -1,11 +1,11 @@
 from __future__ import annotations
 
 from typing import TYPE_CHECKING
+
 from app.services.domains.arxiv.gateway import (
     build_arxiv_query,
     get_arxiv_gateway,
 )
-from app.services.domains.arxiv.errors import ArxivRateLimitError
 
 if TYPE_CHECKING:
     from app.services.domains.publications.types import PublicationListItem, UnreadPublicationItem