Add series browsing, search, and detail UI

Introduce full support for Audible series exploration: API routes, frontend pages, components, hooks, and integrations. Key changes:

- Prisma: add Audiobook.seriesAsin for linking audiobooks to series detail pages.
- Backend: add /api/series/search and /api/series/[asin] routes that require auth; scrape Audible series data and enrich books with library availability.
- Integrations/services: add audible-series integration and update request/HTTP services to support the workflow.
- Frontend: add /series and /series/[asin] pages, new components (SeriesCard, SeriesGrid, SeriesDetailCard, SimilarSeriesRow) and wire them to a new useSeries hook; update AudiobookDetailsModal to show/link series; add Series link to Header.
- Misc: extend audiobook types with series fields and add seriesLabels to language-config for scraping.

These changes enable users to search for series, view series metadata and books, and navigate between audiobook and series detail pages.

src/lib/hooks/useAudiobooks.ts

@@ -20,6 +20,9 @@ export interface Audiobook {
   releaseDate?: string;
   rating?: number;
   genres?: string[];
+  series?: string;         // Series name (e.g., "A Song of Ice and Fire")
+  seriesPart?: string;     // Position in series (e.g., "1", "1.5")
+  seriesAsin?: string;     // Audible ASIN for the series (links to /series/{asin})
   isAvailable?: boolean;  // Set by real-time matching against plex_library
   plexGuid?: string | null;
   dbId?: string | null;