feat(payment): embed Stripe Payment Element inline instead of popup

Stripe payment now shows the Payment Element directly on the purchase
page. User selects payment method (Alipay/WeChat/Card) inline, then
confirms. Redirect-based methods (Alipay) navigate to the payment
page; non-redirect methods (Card/WeChat) complete inline.

frontend/src/components/payment/StripePaymentInline.vue

@@ -0,0 +1,131 @@
+<template>
+  <div class="space-y-4">
+    <div v-if="loading" class="flex items-center justify-center py-12">
+      <div class="h-8 w-8 animate-spin rounded-full border-4 border-primary-500 border-t-transparent"></div>
+    </div>
+    <div v-else-if="initError" class="card p-6 text-center">
+      <p class="text-sm text-red-600 dark:text-red-400">{{ initError }}</p>
+      <button class="btn btn-secondary mt-4" @click="$emit('back')">{{ t('payment.result.backToRecharge') }}</button>
+    </div>
+    <template v-else>
+      <!-- Amount -->
+      <div class="card overflow-hidden">
+        <div class="bg-gradient-to-br from-[#635bff] to-[#4f46e5] px-6 py-5 text-center">
+          <p class="text-sm font-medium text-indigo-200">{{ t('payment.actualPay') }}</p>
+          <p class="mt-1 text-3xl font-bold text-white">&yen;{{ payAmount.toFixed(2) }}</p>
+        </div>
+      </div>
+      <!-- Stripe Payment Element -->
+      <div class="card p-6">
+        <div ref="stripeMount" class="min-h-[200px]"></div>
+        <p v-if="error" class="mt-4 text-sm text-red-600 dark:text-red-400">{{ error }}</p>
+        <div v-if="success" class="mt-4 flex items-center gap-2 text-emerald-600 dark:text-emerald-400">
+          <Icon name="checkCircle" size="md" />
+          <span class="text-sm font-medium">{{ t('payment.stripeSuccessProcessing') }}</span>
+        </div>
+        <button v-if="!success" class="btn btn-stripe mt-6 w-full py-3 text-base" :disabled="submitting || !ready" @click="handlePay">
+          <span v-if="submitting" class="flex items-center justify-center gap-2">
+            <span class="h-4 w-4 animate-spin rounded-full border-2 border-white border-t-transparent"></span>
+            {{ t('common.processing') }}
+          </span>
+          <span v-else>{{ t('payment.stripePay') }}</span>
+        </button>
+      </div>
+      <!-- Back -->
+      <div class="text-center">
+        <button class="btn btn-secondary" @click="$emit('back')">{{ t('payment.result.backToRecharge') }}</button>
+      </div>
+    </template>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { ref, onMounted, onUnmounted, nextTick } from 'vue'
+import { useI18n } from 'vue-i18n'
+import { extractApiErrorMessage } from '@/utils/apiError'
+import type { Stripe, StripeElements } from '@stripe/stripe-js'
+import Icon from '@/components/icons/Icon.vue'
+
+const props = defineProps<{
+  orderId: number
+  clientSecret: string
+  publishableKey: string
+  payAmount: number
+}>()
+
+const emit = defineEmits<{ success: []; back: [] }>()
+
+const { t } = useI18n()
+
+const stripeMount = ref<HTMLElement | null>(null)
+const loading = ref(true)
+const initError = ref('')
+const error = ref('')
+const submitting = ref(false)
+const success = ref(false)
+const ready = ref(false)
+
+let stripeInstance: Stripe | null = null
+let elementsInstance: StripeElements | null = null
+let successTimer: ReturnType<typeof setTimeout> | null = null
+
+onMounted(async () => {
+  try {
+    const { loadStripe } = await import('@stripe/stripe-js')
+    const stripe = await loadStripe(props.publishableKey)
+    if (!stripe) { initError.value = t('payment.stripeLoadFailed'); return }
+
+    stripeInstance = stripe
+    loading.value = false
+    await nextTick()
+    if (!stripeMount.value) return
+
+    const isDark = document.documentElement.classList.contains('dark')
+    const elements = stripe.elements({
+      clientSecret: props.clientSecret,
+      appearance: { theme: isDark ? 'night' : 'stripe', variables: { borderRadius: '8px' } },
+    })
+    elementsInstance = elements
+    const paymentElement = elements.create('payment', {
+      layout: 'tabs',
+      paymentMethodOrder: ['alipay', 'wechat_pay', 'card', 'link'],
+    } as Record<string, unknown>)
+    paymentElement.mount(stripeMount.value)
+    paymentElement.on('ready', () => { ready.value = true })
+  } catch (err: unknown) {
+    initError.value = extractApiErrorMessage(err, t('payment.stripeLoadFailed'))
+  } finally {
+    loading.value = false
+  }
+})
+
+onUnmounted(() => {
+  if (successTimer) clearTimeout(successTimer)
+})
+
+async function handlePay() {
+  if (!stripeInstance || !elementsInstance || submitting.value) return
+  submitting.value = true
+  error.value = ''
+  try {
+    const { error: stripeError } = await stripeInstance.confirmPayment({
+      elements: elementsInstance,
+      confirmParams: {
+        return_url: window.location.origin + '/payment/result?order_id=' + props.orderId + '&status=success',
+      },
+      redirect: 'if_required',
+    })
+    if (stripeError) {
+      error.value = stripeError.message || t('payment.result.failed')
+    } else {
+      // Payment completed without redirect (card, WeChat popup)
+      success.value = true
+      successTimer = setTimeout(() => emit('success'), 1500)
+    }
+  } catch (err: unknown) {
+    error.value = extractApiErrorMessage(err, t('payment.result.failed'))
+  } finally {
+    submitting.value = false
+  }
+}
+</script>

frontend/src/views/user/PaymentView.vue

@@ -26,7 +26,7 @@
             <p class="text-gray-500 dark:text-gray-400">{{ t('payment.notAvailable') }}</p>
           </div>
           <!-- Payment status (replaces selection UI after order creation) -->
-          <template v-else-if="paymentPhase !== 'select'">
+          <template v-else-if="paymentPhase === 'paying'">
             <PaymentStatusPanel
               :order-id="paymentState.orderId"
               :qr-code="paymentState.qrCode"
@@ -37,6 +37,17 @@
               @success="authStore.refreshUser()"
             />
           </template>
+          <!-- Stripe inline payment (select method → confirm → redirect/complete) -->
+          <template v-else-if="paymentPhase === 'stripe'">
+            <StripePaymentInline
+              :order-id="paymentState.orderId"
+              :client-secret="paymentState.clientSecret"
+              :publishable-key="checkout.stripe_publishable_key"
+              :pay-amount="paymentState.payAmount"
+              @success="onStripeSuccess"
+              @back="resetPayment"
+            />
+          </template>
           <!-- Amount & method selection -->
           <template v-else>
           <div class="card p-6">
@@ -144,7 +155,6 @@
 <script setup lang="ts">
 import { ref, computed, onMounted, watch } from 'vue'
 import { useI18n } from 'vue-i18n'
-import { useRouter } from 'vue-router'
 import { useAuthStore } from '@/stores/auth'
 import { usePaymentStore } from '@/stores/payment'
 import { useAppStore } from '@/stores'
@@ -158,11 +168,11 @@ import PaymentMethodSelector from '@/components/payment/PaymentMethodSelector.vu
 import { METHOD_ORDER, POPUP_WINDOW_FEATURES } from '@/components/payment/providerConfig'
 import SubscriptionPlanCard from '@/components/payment/SubscriptionPlanCard.vue'
 import PaymentStatusPanel from '@/components/payment/PaymentStatusPanel.vue'
+import StripePaymentInline from '@/components/payment/StripePaymentInline.vue'
 import Icon from '@/components/icons/Icon.vue'
 import type { PaymentMethodOption } from '@/components/payment/PaymentMethodSelector.vue'
 
 const { t } = useI18n()
-const router = useRouter()
 const authStore = useAuthStore()
 const paymentStore = usePaymentStore()
 const appStore = useAppStore()
@@ -178,13 +188,18 @@ const selectedMethod = ref('')
 const selectedPlan = ref<SubscriptionPlan | null>(null)
 const previewImage = ref('')
 
-// Payment phase: 'select' → 'paying' (after order created)
-const paymentPhase = ref<'select' | 'paying'>('select')
-const paymentState = ref({ orderId: 0, qrCode: '', expiresAt: '', paymentType: '', payUrl: '' })
+// Payment phase: 'select' → 'paying' (QR/redirect) or 'stripe' (inline Stripe)
+const paymentPhase = ref<'select' | 'paying' | 'stripe'>('select')
+const paymentState = ref({ orderId: 0, qrCode: '', expiresAt: '', paymentType: '', payUrl: '', clientSecret: '', payAmount: 0 })
 
 function resetPayment() {
   paymentPhase.value = 'select'
-  paymentState.value = { orderId: 0, qrCode: '', expiresAt: '', paymentType: '', payUrl: '' }
+  paymentState.value = { orderId: 0, qrCode: '', expiresAt: '', paymentType: '', payUrl: '', clientSecret: '', payAmount: 0 }
+}
+
+function onStripeSuccess() {
+  authStore.refreshUser()
+  resetPayment()
 }
 
 // All checkout data from single API call
@@ -313,22 +328,19 @@ async function createOrder(orderAmount: number, orderType: string, planId?: numb
       }
     }
     if (result.client_secret) {
-      // Stripe: open payment page, show waiting state inline
-      const stripeUrl = router.resolve({
-        path: '/payment/stripe',
-        query: { order_id: String(result.order_id), client_secret: result.client_secret },
-      }).href
-      openWindow(stripeUrl)
+      // Stripe: show Payment Element inline (user picks method → confirms → redirect if needed)
       paymentState.value = {
         orderId: result.order_id, qrCode: '', expiresAt: '',
-        paymentType: selectedMethod.value, payUrl: stripeUrl,
+        paymentType: selectedMethod.value, payUrl: '',
+        clientSecret: result.client_secret, payAmount: result.pay_amount,
       }
-      paymentPhase.value = 'paying'
+      paymentPhase.value = 'stripe'
     } else if (result.qr_code) {
       // QR mode: show QR code inline
       paymentState.value = {
         orderId: result.order_id, qrCode: result.qr_code,
         expiresAt: result.expires_at || '', paymentType: selectedMethod.value, payUrl: '',
+        clientSecret: '', payAmount: 0,
       }
       paymentPhase.value = 'paying'
     } else if (result.pay_url) {
@@ -337,6 +349,7 @@ async function createOrder(orderAmount: number, orderType: string, planId?: numb
       paymentState.value = {
         orderId: result.order_id, qrCode: '', expiresAt: result.expires_at || '',
         paymentType: selectedMethod.value, payUrl: result.pay_url,
+        clientSecret: '', payAmount: 0,
       }
       paymentPhase.value = 'paying'
     } else {