feat(backup): admin and account UI for server backups, import by section

Admin settings: switch, time, retention, list with download and a
"Jetzt sichern" button. Account settings: own server backups with
download and restore (replace or add, for chosen sections, replace needs
a second tap). The MindSift import gets the same section picker.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/settings/UserSettingsView.tsx

@@ -19,6 +19,8 @@ import {
 } from 'lucide-react';
 import { AuthStatus, User, UserTheme } from '../../lib/types';
 import { ApiKeysPanel } from './ApiKeysPanel';
+import { ServerBackupsCard } from './ServerBackupsCard';
+import { saveBlob } from '../../lib/download';
 import { api, clearToken, triggerHaptic } from '../../lib/api';
 import { passwordProblem } from '../../lib/password';
 import { customThemeId, ThemeId, ThemeOption } from '../../lib/theme';
@@ -363,16 +365,6 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
 
   // --- Handlers: Export ---
   // Works on mobile browsers too: the link must be in the document and the URL alive until the click ran
-  const saveBlob = (blob: Blob, filename: string) => {
-    const url = URL.createObjectURL(blob);
-    const a = document.createElement('a');
-    a.href = url;
-    a.download = filename;
-    document.body.appendChild(a);
-    a.click();
-    a.remove();
-    window.setTimeout(() => URL.revokeObjectURL(url), 10000);
-  };
 
   const [exportingBackup, setExportingBackup] = useState(false);
   const handleExportData = async () => {
@@ -1166,6 +1158,10 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
 
               <ApiKeysPanel />
 
+              <div className="pt-4 border-t border-border">
+                <ServerBackupsCard />
+              </div>
+
               {/* Full Data Backup */}
               <div className="pt-4 border-t border-border flex flex-col sm:flex-row sm:items-center justify-between gap-3">
                 <div>