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/api/index.js

@@ -0,0 +1,40 @@
+import axios from 'axios'
+import { ElMessage } from 'element-plus'
+import router from '@/router'
+
+const api = axios.create({
+  baseURL: '',
+  timeout: 30000
+})
+
+// 请求拦截器
+api.interceptors.request.use(
+  config => {
+    const token = localStorage.getItem('token')
+    if (token) {
+      config.headers.Authorization = `Bearer ${token}`
+    }
+    return config
+  },
+  error => Promise.reject(error)
+)
+
+// 响应拦截器
+api.interceptors.response.use(
+  response => response,
+  error => {
+    if (error.response?.status === 401) {
+      localStorage.removeItem('token')
+      localStorage.removeItem('user')
+      router.push('/login')
+      ElMessage.error('登录已过期，请重新登录')
+    } else if (error.response?.status === 403) {
+      ElMessage.error('没有权限执行此操作')
+    } else {
+      ElMessage.error(error.response?.data?.detail || error.message || '请求失败')
+    }
+    return Promise.reject(error)
+  }
+)
+
+export default api