fix(payment): integrate recharge fee rate in order flow and fix UI display

Backend:
- Use cfg.RechargeFeeRate in order creation instead of hardcoded 0
- Remove dead getFeeRate stub method
- All amounts computed server-side: order_amount, pay_amount, fee_rate

Frontend - PaymentView:
- Read recharge_fee_rate from checkout-info API (not per-method)
- Show fee breakdown only when fee_rate > 0
- Show credited amount only when multiplier ≠ 1

Frontend - Order display (user + admin):
- Fix fee_rate * 100 bug (fee_rate is already a percentage)
- OrderTable: show pay_amount as primary, fee/credited as sub-lines
- AdminOrderDetail: full breakdown (base/fee/paid/credited)
- AdminRefundDialog: label "到账金额" for clarity
- PaymentResultView: show pay_amount with fee info

Types + i18n:
- Add recharge_fee_rate to CheckoutInfoResponse
- Add fee_rate to CreateOrderResult
- Add translations: creditedAmount, fee, baseAmount, includedInPayAmount

frontend/src/components/admin/payment/AdminOrderDetail.vue

@@ -18,23 +18,27 @@
           </span>
         </div>
         <div>
-          <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.amount') }}</p>
-          <p class="text-sm font-medium text-gray-900 dark:text-white">{{ order.order_type === 'balance' ? '$' : '¥' }}{{ order.amount.toFixed(2) }}</p>
+          <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.baseAmount') }}</p>
+          <p class="text-sm font-medium text-gray-900 dark:text-white">¥{{ baseAmount.toFixed(2) }}</p>
+        </div>
+        <div v-if="order.fee_rate > 0">
+          <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.fee') }} ({{ order.fee_rate }}%)</p>
+          <p class="text-sm font-medium text-gray-900 dark:text-white">¥{{ feeAmount.toFixed(2) }}</p>
         </div>
         <div>
           <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.payAmount') }}</p>
           <p class="text-sm font-medium text-gray-900 dark:text-white">¥{{ order.pay_amount.toFixed(2) }}</p>
         </div>
+        <div v-if="order.amount !== order.pay_amount">
+          <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.creditedAmount') }}</p>
+          <p class="text-sm font-medium text-gray-900 dark:text-white">{{ order.order_type === 'balance' ? '$' : '¥' }}{{ order.amount.toFixed(2) }}</p>
+        </div>
         <div>
           <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.orders.paymentMethod') }}</p>
           <p class="text-sm text-gray-700 dark:text-gray-300">
             {{ t('payment.methods.' + order.payment_type, order.payment_type) }}
           </p>
         </div>
-        <div>
-          <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.admin.feeRate') }}</p>
-          <p class="text-sm text-gray-700 dark:text-gray-300">{{ (order.fee_rate * 100).toFixed(1) }}%</p>
-        </div>
         <div>
           <p class="text-xs text-gray-500 dark:text-gray-400">{{ t('payment.admin.orderType') }}</p>
           <p class="text-sm text-gray-700 dark:text-gray-300">
@@ -110,6 +114,7 @@
 </template>
 
 <script setup lang="ts">
+import { computed } from 'vue'
 import { useI18n } from 'vue-i18n'
 import BaseDialog from '@/components/common/BaseDialog.vue'
 import type { PaymentOrder } from '@/types/payment'
@@ -117,11 +122,24 @@ import { statusBadgeClass, canRefund as canRefundStatus, formatOrderDateTime } f
 
 const { t } = useI18n()
 
-defineProps<{
+const props = defineProps<{
   show: boolean
   order: PaymentOrder | null
 }>()
 
+/** 充值金额 (base amount before fee) = pay_amount - fee = pay_amount / (1 + fee_rate/100) */
+const baseAmount = computed(() => {
+  if (!props.order) return 0
+  if (props.order.fee_rate <= 0) return props.order.pay_amount
+  return props.order.pay_amount / (1 + props.order.fee_rate / 100)
+})
+
+/** 手续费 = pay_amount - baseAmount */
+const feeAmount = computed(() => {
+  if (!props.order || props.order.fee_rate <= 0) return 0
+  return props.order.pay_amount - baseAmount.value
+})
+
 const emit = defineEmits<{
   (e: 'close'): void
   (e: 'cancel', order: PaymentOrder): void

frontend/src/components/admin/payment/AdminOrderTable.vue

@@ -51,12 +51,15 @@
         <span class="text-sm text-gray-600 dark:text-gray-400">#{{ value }}</span>
       </template>
 
-      <template #cell-amount="{ value, row }">
+      <template #cell-pay_amount="{ value, row }">
         <div class="text-sm">
-          <span class="font-medium text-gray-900 dark:text-white">{{ row.order_type === 'balance' ? '$' : '¥' }}{{ value.toFixed(2) }}</span>
-          <span v-if="row.pay_amount !== value" class="ml-1 text-xs text-gray-500">
-            ({{ t('payment.orders.payAmount') }}: ¥{{ row.pay_amount.toFixed(2) }})
+          <span class="font-medium text-gray-900 dark:text-white">¥{{ value.toFixed(2) }}</span>
+          <span v-if="row.fee_rate > 0" class="ml-1 text-xs text-gray-400" :title="t('payment.orders.fee') + ': ' + row.fee_rate + '%'">
+            ({{ row.fee_rate }}%)
           </span>
+          <div v-if="row.amount !== row.pay_amount" class="text-xs text-gray-500">
+            {{ t('payment.orders.creditedAmount') }}: {{ row.order_type === 'balance' ? '$' : '¥' }}{{ row.amount.toFixed(2) }}
+          </div>
         </div>
       </template>
 
@@ -183,7 +186,7 @@ function emitFiltersChanged() {
 const columns = computed<Column[]>(() => [
   { key: 'id', label: t('payment.orders.orderId') },
   { key: 'user_id', label: t('payment.orders.userId') },
-  { key: 'amount', label: t('payment.orders.amount') },
+  { key: 'pay_amount', label: t('payment.orders.payAmount') },
   { key: 'payment_type', label: t('payment.orders.paymentMethod') },
   { key: 'status', label: t('payment.orders.status') },
   { key: 'order_type', label: t('payment.orders.orderType') },

frontend/src/components/admin/payment/AdminRefundDialog.vue

@@ -34,7 +34,7 @@
           <span class="font-mono text-gray-900 dark:text-white">#{{ order?.id }}</span>
         </div>
         <div class="mt-1 flex justify-between text-sm">
-          <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.amount') }}</span>
+          <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.creditedAmount') }}</span>
           <span class="font-medium text-gray-900 dark:text-white">{{ order?.order_type === 'balance' ? '$' : '¥' }}{{ order?.amount?.toFixed(2) }}</span>
         </div>
         <div class="mt-1 flex justify-between text-sm">

frontend/src/components/payment/OrderTable.vue

@@ -12,10 +12,15 @@
         <span v-if="row.user_notes" class="ml-1 text-xs text-gray-400">({{ row.user_notes }})</span>
       </div>
     </template>
-    <template #cell-amount="{ value, row }">
+    <template #cell-pay_amount="{ value, row }">
       <div class="text-sm">
-        <span class="font-medium text-gray-900 dark:text-white">{{ row.order_type === 'balance' ? '$' : '¥' }}{{ value.toFixed(2) }}</span>
-        <span v-if="row.pay_amount !== value" class="ml-1 text-xs text-gray-500">(¥{{ row.pay_amount.toFixed(2) }})</span>
+        <span class="font-medium text-gray-900 dark:text-white">¥{{ value.toFixed(2) }}</span>
+        <span v-if="row.fee_rate > 0" class="ml-1 text-xs text-gray-400" :title="t('payment.orders.fee') + ': ' + row.fee_rate + '%'">
+          ({{ t('payment.orders.fee') }} {{ row.fee_rate }}%)
+        </span>
+        <div v-if="row.amount !== row.pay_amount" class="text-xs text-gray-500">
+          {{ t('payment.orders.creditedAmount') }}: {{ row.order_type === 'balance' ? '$' : '¥' }}{{ row.amount.toFixed(2) }}
+        </div>
       </div>
     </template>
     <template #cell-payment_type="{ value }">
@@ -60,7 +65,7 @@ const columns = computed((): Column[] => {
     cols.push({ key: 'user_email', label: t('payment.admin.colUser') })
   }
   cols.push(
-    { key: 'amount', label: t('payment.orders.amount') },
+    { key: 'pay_amount', label: t('payment.orders.payAmount') },
     { key: 'payment_type', label: t('payment.orders.paymentMethod') },
     { key: 'status', label: t('payment.orders.status') },
     { key: 'created_at', label: t('payment.orders.createdAt') },