refactor: 将 @iconify/vue 图标替换为 lucide-vue-next 本地组件

- 所有 lucide: 前缀的图标字符串替换为 lucide-vue-next 组件直接引用
- 动态图标绑定改为 <component :is> 渲染
- h(Icon, { icon: 'lucide:xxx' }) 改为 h(Xxx, { class: ... })
- app-card.vue 的 icon_url 改为 <img> 标签（实际是图片路径）
- 修复 Webhook 标识符冲突（重命名为 WebhookIcon）
- payment-channels 保留 @iconify/vue 用于品牌图标（支付宝、微信、Stripe、PayPal、USDT）

frontend/src/pages/agent/cards/index.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { Icon } from '@iconify/vue'
+import { Key, Loader2, Plus } from 'lucide-vue-next'
 import { onMounted, ref } from 'vue'
 
 import api from '@/services/api'
@@ -60,7 +60,7 @@ function getStatusBadge(status: string) {
       </div>
       <UiButton as-child>
         <router-link to="/agent/cards/create">
-          <Icon icon="lucide:plus" class="mr-2 h-4 w-4" />
+          <Plus class="mr-2 h-4 w-4" />
           生成卡密
         </router-link>
       </UiButton>
@@ -69,11 +69,11 @@ function getStatusBadge(status: string) {
     <UiCard>
       <UiCardContent class="p-0">
         <div v-if="loading" class="flex items-center justify-center py-12">
-          <Icon icon="lucide:loader-2" class="size-8 animate-spin text-muted-foreground" />
+          <Loader2 class="size-8 animate-spin text-muted-foreground" />
         </div>
 
         <div v-else-if="cards.length === 0" class="text-center py-12 text-muted-foreground">
-          <Icon icon="lucide:key" class="size-16 mx-auto mb-4 opacity-30" />
+          <Key class="size-16 mx-auto mb-4 opacity-30" />
           <p>暂无卡密记录</p>
           <UiButton class="mt-4" as-child>
             <router-link to="/agent/cards/create">