Add custom AI provider support and improve qBittorrent auth

Introduces support for custom OpenAI-compatible AI providers with configurable base URLs, including UI, backend validation, and connection testing. Enhances qBittorrent integration to support HTTP Basic Auth for reverse proxies, adds detailed debug logging, and updates documentation for both features. Also improves login page description logic and AI prompt generation for recommendations.

src/app/login/page.tsx

@@ -38,6 +38,7 @@ function LoginContent() {
     hasLocalUsers: boolean;
     oidcProviderName: string | null;
     localLoginDisabled: boolean;
+    automationEnabled: boolean;
   } | null>(null);
   const [showRegisterForm, setShowRegisterForm] = useState(false);
   const [registerUsername, setRegisterUsername] = useState('');
@@ -77,6 +78,7 @@ function LoginContent() {
           hasLocalUsers: false,
           oidcProviderName: null,
           localLoginDisabled: false,
+          automationEnabled: false,
         });
       }
     };
@@ -519,7 +521,25 @@ function LoginContent() {
             {/* Description */}
             <div className="mb-6 sm:mb-8 text-center">
               <p className="text-gray-400 text-sm sm:text-base">
-                Request audiobooks and they'll automatically download and appear in your Plex library
+                {(() => {
+                  if (!authProviders) return 'Your Personal Audiobook Library Manager';
+
+                  const { backendMode, automationEnabled } = authProviders;
+
+                  // Audiobookshelf mode
+                  if (backendMode === 'audiobookshelf') {
+                    if (automationEnabled) {
+                      return "Request audiobooks and they'll automatically download and appear in your Audiobookshelf library";
+                    }
+                    return "Request audiobooks for your Audiobookshelf library";
+                  }
+
+                  // Plex mode (default)
+                  if (automationEnabled) {
+                    return "Request audiobooks and they'll automatically download and appear in your Plex library";
+                  }
+                  return "Request audiobooks for your Plex library";
+                })()}
               </p>
             </div>