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/package-lock.json

@@ -47,6 +47,7 @@
         "vue-input-otp": "^0.3.2",
         "vue-router": "^5.0.3",
         "vue-sonner": "^2.0.9",
+        "vue3-flag-icons": "^0.1.4",
         "zod": "^4.3.6"
       },
       "devDependencies": {
@@ -7449,6 +7450,12 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/flag-icons": {
+      "version": "7.5.0",
+      "resolved": "https://registry.npmjs.org/flag-icons/-/flag-icons-7.5.0.tgz",
+      "integrity": "sha512-kd+MNXviFIg5hijH766tt+3x76ele1AXlo4zDdCxIvqWZhKt4T83bOtxUOOMlTx/EcFdUMH5yvQgYlFh1EqqFg==",
+      "license": "MIT"
+    },
     "node_modules/flat-cache": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/flat-cache/-/flat-cache-4.0.1.tgz",
@@ -12517,6 +12524,18 @@
         "typescript": ">=5.0.0"
       }
     },
+    "node_modules/vue3-flag-icons": {
+      "version": "0.1.4",
+      "resolved": "https://registry.npmjs.org/vue3-flag-icons/-/vue3-flag-icons-0.1.4.tgz",
+      "integrity": "sha512-bJrrZuVHcs5XCW1CiXG3gpZnkzczk3gXlLgVmKt4XTeKRb3U/qt57hNtTP2ybXEXaigE26WxhO9rVXF9gsL7Dg==",
+      "license": "MIT",
+      "dependencies": {
+        "flag-icons": "^7.2.3"
+      },
+      "peerDependencies": {
+        "vue": "^3.5.0"
+      }
+    },
     "node_modules/webpack-virtual-modules": {
       "version": "0.6.2",
       "resolved": "https://registry.npmjs.org/webpack-virtual-modules/-/webpack-virtual-modules-0.6.2.tgz",