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/services/scheduler.service.test.ts

@@ -78,7 +78,7 @@ describe('SchedulerService', () => {
     const service = new SchedulerService();
     await service.start();
 
-    expect(prismaMock.scheduledJob.create).toHaveBeenCalledTimes(8);
+    expect(prismaMock.scheduledJob.create).toHaveBeenCalledTimes(9);
     expect(jobQueueMock.addRepeatableJob).toHaveBeenCalledWith(
       'audible_refresh',
       { scheduledJobId: 'job-1' },