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/backoffice/lib/i18n/fr.ts

@@ -456,6 +456,40 @@ const fr = {
   "settings.newTargetPlaceholder": "Nouveau statut cible (ex: hiatus)",
   "settings.createTargetStatus": "Créer un statut",
 
+  // Settings - Prowlarr
+  "settings.prowlarr": "Prowlarr",
+  "settings.prowlarrDesc": "Configurer Prowlarr pour rechercher des releases sur les indexeurs (torrents/usenet). Seule la recherche manuelle est disponible pour le moment.",
+  "settings.prowlarrUrl": "URL Prowlarr",
+  "settings.prowlarrUrlPlaceholder": "http://localhost:9696",
+  "settings.prowlarrApiKey": "Clé API",
+  "settings.prowlarrApiKeyPlaceholder": "Clé API Prowlarr",
+  "settings.prowlarrCategories": "Catégories",
+  "settings.prowlarrCategoriesHelp": "ID de catégories Newznab séparés par des virgules (7030 = Comics, 7020 = Ebooks)",
+  "settings.testConnection": "Tester la connexion",
+  "settings.testing": "Test en cours...",
+  "settings.testSuccess": "Connexion réussie",
+  "settings.testFailed": "Échec de la connexion",
+
+  // Prowlarr search modal
+  "prowlarr.searchButton": "Prowlarr",
+  "prowlarr.modalTitle": "Recherche Prowlarr",
+  "prowlarr.searchSeries": "Rechercher la série",
+  "prowlarr.searchVolume": "Rechercher",
+  "prowlarr.searching": "Recherche en cours...",
+  "prowlarr.noResults": "Aucun résultat trouvé",
+  "prowlarr.resultCount": "{{count}} résultat{{plural}}",
+  "prowlarr.missingVolumes": "Volumes manquants",
+  "prowlarr.columnTitle": "Titre",
+  "prowlarr.columnIndexer": "Indexeur",
+  "prowlarr.columnSize": "Taille",
+  "prowlarr.columnSeeders": "Seeds",
+  "prowlarr.columnLeechers": "Peers",
+  "prowlarr.columnProtocol": "Protocole",
+  "prowlarr.searchError": "Erreur lors de la recherche",
+  "prowlarr.notConfigured": "Prowlarr n'est pas configuré",
+  "prowlarr.download": "Télécharger",
+  "prowlarr.info": "Info",
+
   // Settings - Language
   "settings.language": "Langue",
   "settings.languageDesc": "Choisir la langue de l'interface",