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/app/actions/refresh.ts

@@ -1,9 +1,7 @@
 "use server";
 
 import { revalidatePath, revalidateTag } from "next/cache";
-import { LIBRARY_SERIES_CACHE_TAG } from "@/lib/services/library.service";
-
-const HOME_CACHE_TAG = "home-data";
+import { HOME_CACHE_TAG, LIBRARY_SERIES_CACHE_TAG } from "@/constants/cacheConstants";
 
 export type RefreshScope = "home" | "library" | "series";