feat: no-nginx frontend, host nginx config, configurable ports

- Frontend: remove nginx, use serve for static files
- Frontend: add Projects/Milestones/Notifications pages
- Frontend: fix auth endpoint to match backend (/auth/token)
- docker-compose: configurable ports via env vars, reduce frontend resources
- Add nginx-host.conf.example for host-level reverse proxy
- Add .env.example
- Update README with deployment architecture

nginx-host.conf.example

@@ -0,0 +1,26 @@
+# 宿主机 nginx 配置示例
+# 复制到 /etc/nginx/sites-available/ 并 symlink 到 sites-enabled/
+# 修改 server_name 为实际域名
+
+server {
+    listen 80;
+    server_name harborforge.example.com;
+
+    # 前端
+    location / {
+        proxy_pass http://127.0.0.1:3000;
+        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;
+    }
+
+    # API 代理
+    location /api/ {
+        proxy_pass http://127.0.0.1:8000/;
+        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;
+    }
+}