feat: add multi-provider support (Komga + Stripstream Librarian)

- Introduce provider abstraction layer (IMediaProvider, KomgaProvider, StripstreamProvider)
- Add Stripstream Librarian as second media provider with full feature parity
- Migrate all pages and components from direct Komga services to provider factory
- Remove dead service code (BaseApiService, HomeService, LibraryService, SearchService, TestService)
- Fix library/series page-based pagination for both providers (Komga 0-indexed, Stripstream 1-indexed)
- Fix unread filter and search on library page for both providers
- Fix read progress display for Stripstream (reading_status mapping)
- Fix series read status (books_read_count) for Stripstream
- Add global search with series results for Stripstream (series_hits from Meilisearch)
- Fix thumbnail proxy to return 404 gracefully instead of JSON on upstream error
- Replace duration-based cache debug detection with x-nextjs-cache header

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/types/home.ts

@@ -1,9 +1,9 @@
-import type { KomgaBook, KomgaSeries } from "./komga";
+import type { NormalizedBook, NormalizedSeries } from "@/lib/providers/types";
 
 export interface HomeData {
-  ongoing: KomgaSeries[];
-  ongoingBooks: KomgaBook[];
-  recentlyRead: KomgaBook[];
-  onDeck: KomgaBook[];
-  latestSeries: KomgaSeries[];
+  ongoing: NormalizedSeries[];
+  ongoingBooks: NormalizedBook[];
+  recentlyRead: NormalizedBook[];
+  onDeck: NormalizedBook[];
+  latestSeries: NormalizedSeries[];
 }