feat: 添加工具市场前端页面

- 新增 Tools.vue 页面：工具列表、分类筛选、搜索、新建/编辑/删除/测试
- 新增路由 /tools
- 导航菜单添加"工具市场"入口

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/MainLayout.vue

@@ -43,6 +43,10 @@
             <el-icon><Connection /></el-icon>
             <span>数据源管理</span>
           </el-menu-item>
+          <el-menu-item index="tools" @click="router.push('/tools')">
+            <el-icon><Tools /></el-icon>
+            <span>工具市场</span>
+          </el-menu-item>
           <el-menu-item index="model-configs" @click="router.push('/model-configs')">
             <el-icon><Setting /></el-icon>
             <span>模型配置管理</span>
@@ -90,7 +94,7 @@
 import { computed } from 'vue'
 import { useRouter, useRoute } from 'vue-router'
 import { useUserStore } from '@/stores/user'
-import { Document, User, List, Connection, Setting, Star, Lock, Monitor, Bell, Grid, DataAnalysis } from '@element-plus/icons-vue'
+import { Document, User, List, Connection, Setting, Star, Lock, Monitor, Bell, Grid, DataAnalysis, Tools } from '@element-plus/icons-vue'
 
 const router = useRouter()
 const route = useRoute()
@@ -104,6 +108,7 @@ const activeMenu = computed(() => {
   if (route.path === '/agents' || route.path.startsWith('/agents/')) return 'agents'
   if (route.path === '/executions' || route.path.startsWith('/executions/')) return 'executions'
   if (route.path === '/data-sources') return 'data-sources'
+  if (route.path === '/tools') return 'tools'
   if (route.path === '/model-configs') return 'model-configs'
   if (route.path === '/node-templates') return 'node-templates'
   if (route.path === '/permissions') return 'permissions'
@@ -127,6 +132,8 @@ const handleMenuSelect = (key: string) => {
     router.push('/executions')
   } else if (key === 'data-sources') {
     router.push('/data-sources')
+  } else if (key === 'tools') {
+    router.push('/tools')
   } else if (key === 'model-configs') {
     router.push('/model-configs')
   } else if (key === 'node-templates') {