Adding primitive support for likes #12768

[shreya8040]

Closes #12768

Added a likes table to the Open Library database, a openlibrary/core/likes.py model, and a small set of backend API endpoints.

Technical

• Added likes table DDL to scripts/db_setup.py
• Added openlibrary/core/likes.py with Likes class (like, unlike, dislike, get_count, get_for_patron, patron_liked)
• Registered API endpoints in openlibrary/plugins/upstream/code.py:
  • POST /api/like — like or dislike a record (auth required)
  • DELETE /api/like — remove a like (auth required)
  • GET /api/likes — get like/dislike count + patron_liked flag
  • GET /api/patron/likes — get all likes by a patron (paginated)
• Auth enforcement: unauthenticated requests return 401
• Added unit tests covering: like, unlike, double-like idempotency, value constraint, unauthenticated rejection
• Added # TODO comment in likes.py documenting the redirect/merge gap and pointing to resolve_redirects_bulk

Testing

No UI changes — backend only. Run unit tests with:
docker compose run --rm home pytest openlibrary/plugins/openlibrary/tests/test_likes.py

Note: test suite currently blocked by upstream NameError: name 'Locale' is not defined in conftest.py (unrelated to this PR).

Screenshot

Stakeholders

@mekarpeles