Add RDT-Client support and Prowlarr prompt

Introduce RDT-Client integration and related UI/behavior changes.

- Add RDTClientService extending QBittorrentService with RDT-specific behavior (stale-torrent deletion, postProcess cleanup, no-op categories).
- Register 'rdtclient' in supported client types, display names, and protocol mapping; create RDT client factory in DownloadClientManager.
- Add RDT-Client card to DownloadClientManagement UI and placeholder URL in DownloadClientModal.
- Update qbittorrent service: omit per-torrent savepath/sequential options (favor category/automatic management), make several methods protected, and clean up related comments.
- Make organize-files.processor treat rdtclient as a special-case for cleanup (remove local torrent entries after organize).
- Add prowlarr service singleton invalidation and call it when Prowlarr settings are updated so background jobs pick up new credentials.
- Add confirmation flow when changing Prowlarr URL/API key: new useIndexersSettings logic to detect credential changes, prompt ConfirmModal from IndexersTab, and optionally clear configured indexers on confirmed change.

These changes ensure Real-Debrid-backed qBittorrent-compatible clients are supported correctly and that switching Prowlarr credentials is handled safely.

src/lib/services/download-client-manager.service.ts

@@ -16,6 +16,7 @@ import { QBittorrentService } from '@/lib/integrations/qbittorrent.service';
 import { SABnzbdService } from '@/lib/integrations/sabnzbd.service';
 import { NZBGetService } from '@/lib/integrations/nzbget.service';
 import { TransmissionService } from '@/lib/integrations/transmission.service';
+import { RDTClientService } from '@/lib/integrations/rdtclient.service';
 import { PathMappingConfig } from '@/lib/utils/path-mapper';
 import { IDownloadClient, DownloadClientType, ProtocolType, CLIENT_PROTOCOL_MAP, getClientDisplayName } from '@/lib/interfaces/download-client.interface';
 
@@ -193,6 +194,8 @@ export class DownloadClientManager {
         return this.createNZBGetService(config, downloadDir);
       case 'transmission':
         return this.createTransmissionService(config, downloadDir);
+      case 'rdtclient':
+        return this.createRDTClientService(config, downloadDir);
       default:
         throw new Error(`Unsupported download client type: ${config.type}`);
     }
@@ -335,6 +338,29 @@ export class DownloadClientManager {
     );
   }
 
+  /**
+   * Create RDT-Client service instance (same constructor as qBittorrent — identical API)
+   */
+  private createRDTClientService(config: DownloadClientConfig, downloadDir: string): RDTClientService {
+    const pathMapping: PathMappingConfig | undefined = config.remotePathMappingEnabled && config.remotePath && config.localPath
+      ? {
+          enabled: true,
+          remotePath: config.remotePath,
+          localPath: config.localPath,
+        }
+      : undefined;
+
+    return new RDTClientService(
+      config.url,
+      config.username || '',
+      config.password || '',
+      downloadDir,
+      config.category || 'readmeabook',
+      config.disableSSLVerify,
+      pathMapping
+    );
+  }
+
   /**
    * Migrate legacy single-client config to new multi-client format
    */