feat: add admin UI frontend and complete backend APIs

- Add Vue 3 frontend with Element Plus
- Implement login, dashboard, tenant management
- Add app configuration, logs viewer, stats pages
- Add user management for admins
- Update Drone CI to build and deploy frontend
- Frontend ports: 3001 (test), 4001 (prod)

frontend/src/components/Layout.vue

@@ -0,0 +1,105 @@
+<script setup>
+import { computed } from 'vue'
+import { useRouter, useRoute } from 'vue-router'
+import { useAuthStore } from '@/stores/auth'
+import { ElMessageBox } from 'element-plus'
+
+const router = useRouter()
+const route = useRoute()
+const authStore = useAuthStore()
+
+// 菜单项
+const menuItems = computed(() => {
+  const items = [
+    { path: '/dashboard', title: '仪表盘', icon: 'Odometer' },
+    { path: '/tenants', title: '租户管理', icon: 'OfficeBuilding' },
+    { path: '/app-config', title: '应用配置', icon: 'Setting' },
+    { path: '/stats', title: '统计分析', icon: 'TrendCharts' },
+    { path: '/logs', title: '日志查看', icon: 'Document' }
+  ]
+  
+  // 管理员才能看到用户管理
+  if (authStore.isAdmin) {
+    items.push({ path: '/users', title: '用户管理', icon: 'User' })
+  }
+  
+  return items
+})
+
+const activeMenu = computed(() => route.path)
+
+function handleMenuSelect(path) {
+  router.push(path)
+}
+
+function handleLogout() {
+  ElMessageBox.confirm('确定要退出登录吗？', '提示', {
+    confirmButtonText: '确定',
+    cancelButtonText: '取消',
+    type: 'warning'
+  }).then(() => {
+    authStore.logout()
+    router.push('/login')
+  })
+}
+</script>
+
+<template>
+  <div class="layout">
+    <!-- 侧边栏 -->
+    <aside class="sidebar">
+      <div class="logo">
+        <el-icon><Platform /></el-icon>
+        <span style="margin-left: 8px">平台管理</span>
+      </div>
+      
+      <el-menu
+        :default-active="activeMenu"
+        background-color="transparent"
+        text-color="rgba(255,255,255,0.7)"
+        active-text-color="#fff"
+        @select="handleMenuSelect"
+      >
+        <el-menu-item v-for="item in menuItems" :key="item.path" :index="item.path">
+          <el-icon><component :is="item.icon" /></el-icon>
+          <span>{{ item.title }}</span>
+        </el-menu-item>
+      </el-menu>
+    </aside>
+    
+    <!-- 主内容区 -->
+    <div class="main-container">
+      <!-- 顶部栏 -->
+      <header class="header">
+        <div class="breadcrumb">
+          <el-breadcrumb separator="/">
+            <el-breadcrumb-item :to="{ path: '/' }">首页</el-breadcrumb-item>
+            <el-breadcrumb-item v-if="route.meta.title">{{ route.meta.title }}</el-breadcrumb-item>
+          </el-breadcrumb>
+        </div>
+        
+        <div class="user-info">
+          <span class="username">{{ authStore.user?.nickname || authStore.user?.username }}</span>
+          <el-dropdown trigger="click">
+            <el-avatar :size="32">
+              {{ (authStore.user?.nickname || authStore.user?.username || 'U')[0].toUpperCase() }}
+            </el-avatar>
+            <template #dropdown>
+              <el-dropdown-menu>
+                <el-dropdown-item @click="handleLogout">
+                  <el-icon><SwitchButton /></el-icon>
+                  退出登录
+                </el-dropdown-item>
+              </el-dropdown-menu>
+            </template>
+          </el-dropdown>
+        </div>
+      </header>
+      
+      <!-- 内容区 -->
+      <main class="main-content">
+        <router-view />
+      </main>
+    </div>
+  </div>
+</template>