feat: configuration backup management with manual and auto backup

Add backup/restore functionality for the SQLite database. Users can
trigger manual backups, configure automatic backups on an interval
with retention policies, list/download/delete backups, and restore
from any backup.

- Backup engine using VACUUM INTO (safe with WAL mode)
- Backup metadata tracked in DB, files stored in DATA_DIR/backups/
- Settings: backup_enabled, backup_interval_hours, backup_retention_count
- API: POST/GET/DELETE /api/backups, download, restore endpoints
- Autobackup via cron scheduler with configurable interval
- Retention: prune on startup, after each backup (manual and auto)
- Orphan cleanup: removes backup files without metadata on startup
- Restore: replaces DB and triggers graceful server shutdown
- Settings UI: /settings/backup with toggle, interval, retention config
- Backup list with download, delete, restore actions
- i18n: English and Russian translations

web/src/lib/api.ts

@@ -24,7 +24,8 @@ import type {
 	VolumeScopeInfo,
 	BrowseResult,
 	DnsZone,
-	DnsRecordView
+	DnsRecordView,
+	BackupInfo
 } from './types';
 
 // ── Helpers ─────────────────────────────────────────────────────────
@@ -292,6 +293,28 @@ export function deleteDnsRecord(fqdn: string): Promise<void> {
 	return del<void>(`/api/dns/records/${encodeURIComponent(fqdn)}`);
 }
 
+// ── Backups ────────────────────────────────────────────────────────
+
+export function listBackups(): Promise<BackupInfo[]> {
+	return get<BackupInfo[]>('/api/backups');
+}
+
+export function triggerBackup(): Promise<BackupInfo> {
+	return post<BackupInfo>('/api/backups');
+}
+
+export function deleteBackup(id: string): Promise<void> {
+	return del<void>(`/api/backups/${id}`);
+}
+
+export function restoreBackup(id: string): Promise<{ status: string; message: string }> {
+	return post<{ status: string; message: string }>(`/api/backups/${id}/restore`);
+}
+
+export function backupDownloadUrl(id: string): string {
+	return `/api/backups/${id}/download`;
+}
+
 // ── Health ──────────────────────────────────────────────────────────
 
 export function getHealth(): Promise<{ docker: DockerHealth }> {