feat: add Prowlarr integration for manual release search

Add Prowlarr indexer integration (step 1: config + manual search).
Allows searching for comics/ebooks releases on Prowlarr indexers
directly from the series detail page, with download links and
per-volume search for missing books.

- Backend: new prowlarr module with search and test endpoints
- Migration: add prowlarr settings (url, api_key, categories)
- Settings UI: Prowlarr config card with test connection button
- ProwlarrSearchModal: auto-search on open, missing volumes shortcuts
- Fix series.readCount i18n plural parameter on series pages

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

apps/api/src/main.rs

@@ -12,6 +12,7 @@ mod metadata_providers;
 mod api_middleware;
 mod openapi;
 mod pages;
+mod prowlarr;
 mod reading_progress;
 mod search;
 mod settings;
@@ -104,6 +105,8 @@ async fn main() -> anyhow::Result<()> {
         .route("/admin/tokens", get(tokens::list_tokens).post(tokens::create_token))
         .route("/admin/tokens/:id", delete(tokens::revoke_token))
         .route("/admin/tokens/:id/delete", axum::routing::post(tokens::delete_token))
+        .route("/prowlarr/search", axum::routing::post(prowlarr::search_prowlarr))
+        .route("/prowlarr/test", get(prowlarr::test_prowlarr))
         .route("/komga/sync", axum::routing::post(komga::sync_komga_read_books))
         .route("/komga/reports", get(komga::list_sync_reports))
         .route("/komga/reports/:id", get(komga::get_sync_report))