Retry catalog searches without FTS on MATCH failure

[Jamesllllllllll]

Summary

Follow-up to #18 and #62.

Prevent viewer request submission from failing when the catalog FTS MATCH query errors on a streamer-choice search such as Smashing Pumpkins.

What Changed

• Switched the generated catalog FTS query to explicit AND-joined prefix terms.
• Added a fallback path in searchCatalogSongs that retries the same search without FTS if the MATCH query fails.
• Added a regression test that simulates an FTS failure and verifies we still return results through the LIKE-based search path.

How To Test

1. Open the public playlist page for a channel.
2. Submit a regular streamer-choice request such as Smashing Pumpkins from the request panel.
3. Confirm the request succeeds instead of returning the SQL error from /api/channel/:slug/viewer-request.
4. Run npm run typecheck and npm run test -- tests/catalog-search.test.ts tests/viewer-request.test.ts.
5. Run npm run check:prepush.

Screenshots Or UI Notes

No visible UI change. This is a backend search fallback fix.

Checklist

• I tested the change locally
• I updated docs or examples if needed
• I called out any follow-up work or known limitations

[github-actions]

Preview deployment updated.

App: https://request-bot-pr-63.jameskeezer.workers.dev
Frontend worker: request-bot-pr-63
Backend worker: request-bot-backend-pr-63