feat(vm-ops): make reinstall/clone/change-password async via DeployTask

Backend:
- Add DeployTask.kind column ('deploy'|'reinstall'|'clone'|'change_password')
  + Migration 23: ALTER TABLE deploy_tasks ADD kind, drop NOT NULL on template_id
- Update DeployTask.to_dict() with kind-aware Russian descriptions
- New backend/app/api/proxmox/async_ops.py with three workers:
    _do_reinstall_sync, _do_clone_sync, _do_change_password_sync
  All run on shared _deploy_executor thread pool from templates.py and
  report progress through _update_deploy_task (DB + WebSocket broadcast)
- Rewrite five vms.py endpoints to return 202 + DeployTaskStartResponse:
    POST /vm/{vmid}/clone, /container/{vmid}/clone,
    POST /vm/{vmid}/reinstall,
    POST /vm/{vmid}/change-password, /container/{vmid}/change-password

Frontend:
- DeployTask: add 'kind' and 'server_id' fields
- useCloneInstance/useReinstallInstance/useChangePassword now return
  AsyncTaskResponse {task_id, status, name}; remove invalidateQueries
- InstanceActionDialogs: each onSuccess pushes task to deploy-tasks-store
  with appropriate kind, shows 'launched in background' toast
- InstancesPage:
  * ghostRows only for kind in {deploy, clone}, deduped by (server_id, vmid)
  * reinstall / change_password tasks shown as inline overlay (badge + ring)
    on the existing VM row's status column

backend/app/api/templates.py

@@ -58,6 +58,7 @@ class DeployTaskStatusResponse(BaseModel):
     created_at: Optional[str]
     started_at: Optional[str]
     completed_at: Optional[str]
+    kind: Optional[str] = 'deploy'
 
 
 # ==================== Template Groups CRUD ====================