Add watched series/authors feature

Introduce watched lists for series and authors end-to-end.

- Add DB migration to create watched_series and watched_authors tables with indexes and foreign keys.
- Implement API routes: GET/POST for listing/adding and DELETE by id for both /api/user/watched-series and /api/user/watched-authors. Validation, ownership checks, and immediate targeted job triggers are included.
- Add client hooks (useWatchedSeries, useWatchedAuthors) with add/delete helpers and SWR revalidation.
- Add UI components: WatchButton (toggle/confirm) and WatchedListsSection for profile display and removal UX.
- Add processor (check-watched-lists.processor) and service (watched-lists.service) to scrape Audible, deduplicate, check library ownership, and auto-create requests; supports targeted checks for newly watched items.
- Include tests for the watched-lists service.

These changes implement the watched-lists feature to let users watch series/authors and have the system automatically detect and request new releases.

tests/helpers/prisma.ts

@@ -49,6 +49,8 @@ export const createPrismaMock = () => ({
   goodreadsBookMapping: createModelMock(),
   work: createModelMock(),
   workAsin: createModelMock(),
+  watchedSeries: createModelMock(),
+  watchedAuthor: createModelMock(),
   $queryRaw: vi.fn(),
   $disconnect: vi.fn(),
 });