Add extensible notification providers + UI/API

Introduce a provider-based notification system and wire it through the API and admin UI. Added INotificationProvider + notification service implementation and providers (apprise, discord, ntfy, pushover), plus a GET /api/admin/notifications/providers endpoint to expose provider metadata. Refactored code to use provider type strings (removed enum coupling), updated masking/encryption calls, and simplified the test notification endpoint to accept backendId or type+config and call sendToBackend directly.

UI: NotificationsTab now fetches provider metadata and renders provider cards and dynamic config forms (fields driven by provider metadata). Added config field rendering, improved backend cards, and edit/delete actions.

APIs: New providers route, updated admin notification CRUD routes to validate provider types dynamically, updated test route schema. Added download-client categories POST API to fetch categories from clients and wired postImportCategory handling in download-client routes.

Other notable changes: BookDate now fetches Claude models dynamically from Anthropic's Models API; added paginated model fetch helper. Added ALLOW_WEAK_PASSWORD flag exposure to auth providers and password change logic. Doc updates and various tests added/updated. File-organization doc clarifies EPERM fix using stream-based copy.

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

@@ -10,7 +10,7 @@ import { Modal } from '@/components/ui/Modal';
 import { Button } from '@/components/ui/Button';
 import { Input } from '@/components/ui/Input';
 import { fetchWithAuth } from '@/lib/utils/api';
-import { DownloadClientType, getClientDisplayName } from '@/lib/interfaces/download-client.interface';
+import { DownloadClientType, getClientDisplayName, CLIENT_PROTOCOL_MAP } from '@/lib/interfaces/download-client.interface';
 
 interface DownloadClientModalProps {
   isOpen: boolean;
@@ -31,6 +31,7 @@ interface DownloadClientModalProps {
     localPath?: string;
     category?: string;
     customPath?: string;
+    postImportCategory?: string;
   };
   onSave: (client: any) => Promise<void>;
   apiMode: 'wizard' | 'settings';
@@ -62,6 +63,9 @@ export function DownloadClientModal({
   const [localPath, setLocalPath] = useState('');
   const [category, setCategory] = useState('readmeabook');
   const [customPath, setCustomPath] = useState('');
+  const [postImportCategory, setPostImportCategory] = useState('');
+  const [availableCategories, setAvailableCategories] = useState<string[]>([]);
+  const [fetchingCategories, setFetchingCategories] = useState(false);
 
   const [testing, setTesting] = useState(false);
   const [saving, setSaving] = useState(false);
@@ -85,6 +89,7 @@ export function DownloadClientModal({
         setLocalPath(initialClient.localPath || '');
         setCategory(initialClient.category || 'readmeabook');
         setCustomPath(initialClient.customPath || '');
+        setPostImportCategory(initialClient.postImportCategory || '');
       } else {
         // Add mode defaults
         setName(typeName);
@@ -98,9 +103,12 @@ export function DownloadClientModal({
         setLocalPath('');
         setCategory('readmeabook');
         setCustomPath('');
+        setPostImportCategory('');
       }
       setTestResult(null);
       setErrors({});
+      setAvailableCategories([]);
+      setFetchingCategories(false);
     }
   }, [isOpen, mode, initialClient, type]);
 
@@ -137,6 +145,50 @@ export function DownloadClientModal({
     return Object.keys(newErrors).length === 0;
   };
 
+  const fetchCategories = async () => {
+    setFetchingCategories(true);
+    try {
+      const isPasswordMasked = password === '********';
+      const categoryData = {
+        type,
+        name,
+        url,
+        username: username || undefined,
+        password: isPasswordMasked ? undefined : password,
+        ...(mode === 'edit' && initialClient && isPasswordMasked ? { clientId: initialClient.id } : {}),
+        disableSSLVerify,
+        remotePathMappingEnabled,
+        remotePath: remotePathMappingEnabled ? remotePath : undefined,
+        localPath: remotePathMappingEnabled ? localPath : undefined,
+      };
+
+      const endpoint = apiMode === 'wizard'
+        ? '/api/setup/download-client-categories'
+        : '/api/admin/settings/download-clients/categories';
+
+      const response = apiMode === 'wizard'
+        ? await fetch(endpoint, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(categoryData),
+          })
+        : await fetchWithAuth(endpoint, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(categoryData),
+          });
+
+      const data = await response.json();
+      if (response.ok && data.success) {
+        setAvailableCategories(data.categories || []);
+      }
+    } catch {
+      // Non-critical — categories are optional
+    } finally {
+      setFetchingCategories(false);
+    }
+  };
+
   const handleTestConnection = async () => {
     if (!validate()) {
       return;
@@ -187,6 +239,11 @@ export function DownloadClientModal({
         // Handle both endpoint response formats (settings returns message, wizard returns version)
         const message = data.message || (data.version ? `Connected successfully (v${data.version})` : 'Connection successful');
         setTestResult({ success: true, message });
+
+        // Fetch categories for torrent clients after successful connection
+        if (type && CLIENT_PROTOCOL_MAP[type] === 'torrent') {
+          fetchCategories();
+        }
       } else {
         setTestResult({ success: false, message: data.error || 'Connection test failed' });
       }
@@ -230,6 +287,7 @@ export function DownloadClientModal({
         localPath: remotePathMappingEnabled ? localPath : undefined,
         category,
         customPath: sanitizedCustomPath || undefined,
+        postImportCategory,
       };
 
       if (mode === 'edit' && initialClient) {
@@ -384,6 +442,37 @@ export function DownloadClientModal({
           </p>
         </div>
 
+        {/* Post-Import Category (torrent clients only) */}
+        {type && CLIENT_PROTOCOL_MAP[type] === 'torrent' && (
+          <div>
+            <label className="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
+              Post-Import Category
+            </label>
+            {type === 'qbittorrent' && availableCategories.length > 0 ? (
+              <select
+                value={postImportCategory}
+                onChange={(e) => setPostImportCategory(e.target.value)}
+                className="w-full rounded-md border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-700 text-gray-900 dark:text-gray-100 px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-transparent"
+              >
+                <option value="">None (keep original)</option>
+                {availableCategories.map((cat) => (
+                  <option key={cat} value={cat}>{cat}</option>
+                ))}
+              </select>
+            ) : (
+              <Input
+                value={postImportCategory}
+                onChange={(e) => setPostImportCategory(e.target.value)}
+                placeholder="e.g. completed"
+                disabled={fetchingCategories}
+              />
+            )}
+            <p className="mt-1 text-xs text-gray-500 dark:text-gray-400">
+              After import, change the download&apos;s category/label in the client. Leave empty to skip.
+            </p>
+          </div>
+        )}
+
         {/* Remote Path Mapping */}
         <div className="border-t border-gray-200 dark:border-gray-700 pt-4">
           <div className="flex items-start mb-3">