fix: merge general improvements from release branch

Backend:
- gateway_handler: pass subject.UserID instead of int64(0) for user-level routing
- setting_handler: add missing BalanceLowNotifyRechargeURL to UpdateSettings response
- openai_gateway_service: use applyAccountStatsCost for account stats pricing integration
- embed_on: add local file override (data/public/) for embedded frontend assets

Frontend:
- useTableSelection: add batchUpdate method for batch operations
- AccountsView: virtual scrolling params, Set-based isSelected, swipe virtualization
- ProxiesView: add batchUpdate to selection and swipe-select
- BulkEditAccountModal: fix submit handler to prevent event object as argument
- SettingsView: move payload construction outside try block
- i18n: add general translation keys (saved, deleted, view, validation, allowUserRefund)
- api/client: reorder error fields for consistency
- stores/payment: clarify pollOrderStatus JSDoc

frontend/src/views/admin/ProxiesView.vue

@@ -985,7 +985,8 @@ const {
   deselect,
   clear: clearSelectedProxies,
   removeMany: removeSelectedProxies,
-  toggleVisible
+  toggleVisible,
+  batchUpdate
 } = useTableSelection<Proxy>({
   rows: proxies,
   getId: (proxy) => proxy.id
@@ -993,7 +994,8 @@ const {
 useSwipeSelect(proxyTableRef, {
   isSelected,
   select,
-  deselect
+  deselect,
+  batchUpdate
 })
 const accountsProxy = ref<Proxy | null>(null)
 const proxyAccounts = ref<ProxyAccountSummary[]>([])