feat: multi-database backup, HTTP API endpoints, admin panel UI

- backup CLI: add --all-databases, --database, --data-root flags
- backup format: tar.gz with databases/<name>/ + backup.json metadata
- HTTP API: new endpoints /databases, /backup, /backups, /restore
- HTTP API: database switching via X-Database header
- Admin panel: database selector dropdown, Databases tab, Backups tab
- Admin panel: backup/restore UI with fetch() to new endpoints
- Update deps: hunos 1.3.0, jwt-nim-baraba 2.1.0
- Docker: backup cron uses --all-databases --data-root=/data/databases
- Docs: update api-http.md, protocol.md with correct endpoints
- OpenAPI spec updated to v1.1.6

Known limitation: DELETE /databases disabled due to ORC SIGSEGV
in LSMTree.close(). Use SQL DROP DATABASE instead.

docs/en/protocol.md

@@ -290,9 +290,19 @@ Response:
 ```http
 POST /backup
 Content-Type: application/json
+Authorization: Bearer <token>
 
 {
-  "destination": "/backup/snapshot.db"
+  "all": true
+}
+```
+
+Response:
+```json
+{
+  "success": true,
+  "output": "backup_1234567890.tar.gz",
+  "message": "Backup created"
 }
 ```