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/SettingsView.vue

@@ -4116,12 +4116,13 @@ async function handleToggleField(provider: ProviderInstance, field: 'enabled' |
   if (field === 'enabled') newValue = !provider.enabled
   else if (field === 'refund_enabled') newValue = !provider.refund_enabled
   else newValue = !provider.allow_user_refund
+
+  const payload: Record<string, boolean> = { [field]: newValue }
+  // Cascade: turning off refund_enabled also turns off allow_user_refund
+  if (field === 'refund_enabled' && !newValue) {
+    payload.allow_user_refund = false
+  }
   try {
-    const payload: Record<string, boolean> = { [field]: newValue }
-    // Cascade: turning off refund_enabled also disables allow_user_refund
-    if (field === 'refund_enabled' && !newValue) {
-      payload.allow_user_refund = false
-    }
     await adminAPI.payment.updateProvider(provider.id, payload)
     if (field === 'enabled') provider.enabled = newValue
     else if (field === 'refund_enabled') {