fix(payment): show full amount breakdown on payment result page

- Show base amount (充值金额) as first line
- Show fee amount with percentage when fee_rate > 0
- Show pay_amount (实付金额) in bold primary color
- Show credited amount (到账金额) when different from pay_amount
- Compute baseAmount and feeAmount from backend order data

frontend/src/views/user/PaymentResultView.vue

@@ -37,12 +37,16 @@
               <span class="font-medium text-gray-900 dark:text-white">{{ order.out_trade_no }}</span>
             </div>
             <div class="flex justify-between">
-              <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.payAmount') }}</span>
-              <span class="font-medium text-gray-900 dark:text-white">&#165;{{ order.pay_amount.toFixed(2) }}</span>
+              <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.baseAmount') }}</span>
+              <span class="font-medium text-gray-900 dark:text-white">&#165;{{ baseAmount.toFixed(2) }}</span>
             </div>
             <div v-if="order.fee_rate > 0" class="flex justify-between">
               <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.fee') }} ({{ order.fee_rate }}%)</span>
-              <span class="text-xs text-gray-400 dark:text-gray-500">{{ t('payment.orders.includedInPayAmount') }}</span>
+              <span class="font-medium text-gray-900 dark:text-white">&#165;{{ feeAmount.toFixed(2) }}</span>
+            </div>
+            <div class="flex justify-between">
+              <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.payAmount') }}</span>
+              <span class="font-bold text-primary-600 dark:text-primary-400">&#165;{{ order.pay_amount.toFixed(2) }}</span>
             </div>
             <div v-if="order.amount !== order.pay_amount" class="flex justify-between">
               <span class="text-gray-500 dark:text-gray-400">{{ t('payment.orders.creditedAmount') }}</span>
@@ -112,6 +116,18 @@ const returnInfo = ref<ReturnInfo | null>(null)
 
 const SUCCESS_STATUSES = new Set(['COMPLETED', 'PAID', 'RECHARGING'])
 
+/** 充值金额 = pay_amount / (1 + fee_rate/100)，fee_rate=0 时等于 pay_amount */
+const baseAmount = computed(() => {
+  if (!order.value || order.value.fee_rate <= 0) return order.value?.pay_amount ?? 0
+  return Math.round((order.value.pay_amount / (1 + order.value.fee_rate / 100)) * 100) / 100
+})
+
+/** 手续费 = pay_amount - baseAmount */
+const feeAmount = computed(() => {
+  if (!order.value || order.value.fee_rate <= 0) return 0
+  return Math.round((order.value.pay_amount - baseAmount.value) * 100) / 100
+})
+
 const isSuccess = computed(() => {
   // Always prioritize actual order status from backend
   if (order.value) {