Add per-user ignored audiobooks feature

Introduce a per-user "ignored audiobooks" feature to suppress auto-requests. Changes include:

- Database: add Prisma model IgnoredAudiobook and SQL migration to create ignored_audiobooks table with indexes and FK to users.
- Backend: new API routes to list, add, delete, and check ignored audiobooks (/api/user/ignored-audiobooks, /check/:asin, /:id). Add annotateWithIgnoreStatus utility and integrate it into multiple audiobook list endpoints (popular, new-releases, category, search, authors, series).
- Request creator: add ignore-list check (with sibling-ASIN expansion) and a bypassIgnore option for manual requests; return an 'ignored' reason when blocked.
- Frontend: hooks (useIsIgnored, useToggleIgnore, useIgnoredList) and UI updates — AudiobookCard shows an "Ignored" indicator and AudiobookDetailsModal adds an ignore toggle and propagates local state changes.
- Misc: adjust deduplication duration tolerance (to 5% / min 10 minutes), tweak SWR refresh intervals for shelves/syncing, and small logging/info updates.
- Tests: add unit tests for request-creator ignore logic and update existing tests/mocks to account for ignore annotation; extend prisma test helper with ignoredAudiobook mock.

This commit implements the ignore-list end-to-end (DB, server, client, and tests) so users can ignore specific ASINs and have auto-request flows respect that preference.

prisma/schema.prisma

@@ -74,6 +74,7 @@ model User {
   watchedSeries           WatchedSeries[]
   watchedAuthors          WatchedAuthor[]
   homeSections            UserHomeSection[]
+  ignoredAudiobooks       IgnoredAudiobook[]
 
   @@index([plexId])
   @@index([role])
@@ -675,6 +676,32 @@ model WatchedAuthor {
   @@map("watched_authors")
 }
 
+// ============================================================================
+// IGNORED AUDIOBOOK TABLE
+// Per-user ignore list for auto-request suppression.
+// Stores the ASIN the user clicked ignore on; works-system expansion
+// happens at check-time in request-creator.service.ts.
+// Documentation: documentation/features/ignored-audiobooks.md
+// ============================================================================
+
+model IgnoredAudiobook {
+  id          String   @id @default(uuid())
+  userId      String   @map("user_id")
+  asin        String   // Audible ASIN that was explicitly ignored
+  title       String   // Display only — snapshot at ignore time
+  author      String   // Display only — snapshot at ignore time
+  coverArtUrl String?  @map("cover_art_url") @db.Text
+  createdAt   DateTime @default(now()) @map("created_at")
+
+  // Relations
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+
+  @@unique([userId, asin])
+  @@index([userId])
+  @@index([asin])
+  @@map("ignored_audiobooks")
+}
+
 // ============================================================================
 // USER HOME SECTION TABLE
 // Per-user configurable home page sections (popular, new_releases, category)