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/components/admin/download-clients/DownloadClientManagement.tsx

@@ -253,7 +253,7 @@ export function DownloadClientManagement({
         <h3 className="text-lg font-semibold text-gray-900 dark:text-gray-100 mb-3">
           Add Download Client
         </h3>
-        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-4">
+        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-5 gap-4">
           {/* qBittorrent Card */}
           <div className={`bg-white dark:bg-gray-800 rounded-lg shadow-md border border-gray-200 dark:border-gray-700 p-6${hasTorrentClient ? ' opacity-50' : ''}`}>
             <div className="flex items-start justify-between mb-3">
@@ -316,6 +316,37 @@ export function DownloadClientManagement({
             )}
           </div>
 
+          {/* RDT-Client Card */}
+          <div className={`bg-white dark:bg-gray-800 rounded-lg shadow-md border border-gray-200 dark:border-gray-700 p-6${hasTorrentClient ? ' opacity-50' : ''}`}>
+            <div className="flex items-start justify-between mb-3">
+              <div>
+                <h4 className="text-base font-semibold text-gray-900 dark:text-gray-100 mb-1">
+                  RDT-Client
+                </h4>
+                <p className="text-sm text-gray-600 dark:text-gray-400">
+                  Torrent / Debrid
+                </p>
+              </div>
+              <span className="inline-block text-xs px-2 py-1 rounded bg-teal-100 dark:bg-teal-900/30 text-teal-700 dark:text-teal-300 font-medium">
+                Torrent
+              </span>
+            </div>
+            {hasTorrentClient ? (
+              <div className="text-sm text-gray-500 dark:text-gray-400">
+                Protocol already configured
+              </div>
+            ) : (
+              <Button
+                onClick={() => handleAddClient('rdtclient')}
+                variant="primary"
+                size="sm"
+                disabled={loading}
+              >
+                Add RDT-Client
+              </Button>
+            )}
+          </div>
+
           {/* SABnzbd Card */}
           <div className={`bg-white dark:bg-gray-800 rounded-lg shadow-md border border-gray-200 dark:border-gray-700 p-6${hasUsenetClient ? ' opacity-50' : ''}`}>
             <div className="flex items-start justify-between mb-3">

src/components/admin/download-clients/DownloadClientModal.tsx

@@ -338,7 +338,7 @@ export function DownloadClientModal({
           <Input
             value={url}
             onChange={(e) => setUrl(e.target.value)}
-            placeholder={type === 'transmission' ? 'http://localhost:9091' : type === 'qbittorrent' ? 'http://localhost:8080' : type === 'nzbget' ? 'http://localhost:6789' : 'http://localhost:8081'}
+            placeholder={type === 'rdtclient' ? 'http://localhost:6500' : type === 'transmission' ? 'http://localhost:9091' : type === 'qbittorrent' ? 'http://localhost:8080' : type === 'nzbget' ? 'http://localhost:6789' : 'http://localhost:8081'}
             error={errors.url}
           />
           <p className="mt-1 text-xs text-gray-500 dark:text-gray-400">