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/lib/api.ts

@@ -4,6 +4,8 @@ import {
   DashboardStats,
   Document,
   TrashedDocument,
+  BackupFile,
+  DataSection,
   ApiKeyScope,
   Backlink,
   DocumentBlock,
@@ -1155,7 +1157,8 @@ export const api = {
     source: 'mindsift' | 'obsidian',
     file: File,
     preview: boolean,
-    mode: 'merge' | 'restore' = 'merge'
+    mode: 'merge' | 'restore' = 'merge',
+    sections?: DataSection[]
   ): Promise<ImportSummary> {
     const token = getToken();
     const form = new FormData();
@@ -1163,6 +1166,7 @@ export const api = {
     const params = new URLSearchParams();
     if (preview) params.set('preview', '1');
     if (mode === 'restore') params.set('mode', 'restore');
+    if (sections && sections.length > 0) params.set('sections', sections.join(','));
     const res = await fetch(`/api/v1/import/${source}${params.toString() ? `?${params}` : ''}`, {
       method: 'POST',
       headers: token ? { Authorization: `Bearer ${token}` } : {},
@@ -1173,6 +1177,33 @@ export const api = {
     return data as ImportSummary;
   },
 
+  // --- Automatic server backups ---
+  async adminListBackups(): Promise<BackupFile[]> {
+    return ensureArray(await request<BackupFile[]>('/api/v1/admin/backups'));
+  },
+
+  async adminRunBackup(): Promise<BackupFile[]> {
+    return ensureArray(await request<BackupFile[]>('/api/v1/admin/backups', { method: 'POST' }));
+  },
+
+  async adminDownloadBackup(name: string): Promise<Blob> {
+    return downloadBlob(`/api/v1/admin/backups/${encodeURIComponent(name)}`);
+  },
+
+  async listMyBackups(): Promise<BackupFile[]> {
+    return ensureArray(await request<BackupFile[]>('/api/v1/backups'));
+  },
+
+  async downloadMyBackup(name: string): Promise<Blob> {
+    return downloadBlob(`/api/v1/backups/${encodeURIComponent(name)}`);
+  },
+
+  async restoreMyBackup(name: string, mode: 'merge' | 'restore', sections: DataSection[], preview = false): Promise<ImportSummary> {
+    const params = new URLSearchParams({ mode, sections: sections.join(',') });
+    if (preview) params.set('preview', '1');
+    return request<ImportSummary>(`/api/v1/backups/${encodeURIComponent(name)}/restore?${params}`, { method: 'POST' });
+  },
+
   // Danger zone: both need the current password
   async purgeOwnData(password: string): Promise<void> {
     await request('/api/v1/user/data', { method: 'DELETE', body: JSON.stringify({ password }) });