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/components/reader/ClientBookReader.tsx

@@ -2,12 +2,12 @@
 
 import { useState } from "react";
 import { useRouter } from "next/navigation";
-import type { KomgaBook } from "@/types/komga";
+import type { NormalizedBook } from "@/lib/providers/types";
 import { PhotoswipeReader } from "./PhotoswipeReader";
 import { Button } from "@/components/ui/button";
 
 interface ClientBookReaderProps {
-  book: KomgaBook;
+  book: NormalizedBook;
   pages: number[];
 }