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)

deploy/Dockerfile.frontend

@@ -0,0 +1,21 @@
+FROM node:20-alpine as builder
+
+WORKDIR /app
+
+# 安装依赖
+COPY frontend/package*.json ./
+RUN npm ci
+
+# 构建
+COPY frontend/ .
+RUN npm run build
+
+# 生产镜像
+FROM nginx:alpine
+
+COPY --from=builder /app/dist /usr/share/nginx/html
+COPY deploy/nginx/frontend.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]

deploy/nginx/frontend.conf

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+server {
+    listen 80;
+    server_name localhost;
+    
+    root /usr/share/nginx/html;
+    index index.html;
+    
+    # Vue Router history mode
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+    
+    # API 代理到后端
+    location /api/ {
+        proxy_pass http://172.17.0.1:8001/api/;
+        proxy_http_version 1.1;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_read_timeout 120s;
+    }
+    
+    # 静态资源缓存
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2)$ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+    }
+    
+    # 禁止访问隐藏文件
+    location ~ /\. {
+        deny all;
+    }
+}