Feature: Support subpath deployment for Go web UI

Add optional YAMA_WEB_BASE_PATH to mount the whole web UI (index, manifest,
static assets, /health, /api/devices, /ws) under a URL prefix such as
/remoter behind a reverse proxy. index.html now uses a __BASE_PATH__
placeholder substituted at serve time, the PWA manifest start_url is rooted
at the base path, and a mount wrapper redirects the bare prefix to prefix/
and strips it before routing. Include nginx, systemd, and env-file deployment
examples for the subpath setup.

The shared placeholder is also handled by the MFC server, which serves from
the domain root and strips __BASE_PATH__ (to "") so its web remote desktop
URLs stay rooted.

Co-Authored-By: deepseek-v4-pro

server/go/deploy/nginx-yama.conf.example

@@ -0,0 +1,68 @@
+# ============================================================
+#  YAMA 网页端 nginx 反代示例（方案B：子路径部署）
+#  作为站点配置放入 /etc/nginx/sites-available/yama 后软链到 sites-enabled
+#  核心原则：nginx 只做 TLS 终止 + 完整路径转发，由 Go 端
+#            YAMA_WEB_BASE_PATH=/remoter 负责 strip
+# ============================================================
+
+server {
+    listen 443 ssl http2;
+    server_name 你的域名.com;
+
+    # TLS 证书（路径换成你自己的，如 certbot/letsencrypt 生成的位置）
+    ssl_certificate     /etc/letsencrypt/live/你的域名.com/fullchain.pem;
+    ssl_certificate_key /etc/letsencrypt/live/你的域名.com/privkey.pem;
+
+    # 裸 /remoter（没写结尾斜杠）→ 301 到 /remoter/
+    location = /remoter {
+        return 301 /remoter/;
+    }
+
+    # 子路径：完整路径原样转发，Go 端按 YAMA_WEB_BASE_PATH 再 strip
+    location /remoter/ {
+        # 结尾没有 "/" → /remoter/... 原样转发（不要写成 http://127.0.0.1:8080/）
+        # Go 服务端若在另一台机器，换成 http://192.168.1.50:8080;
+        proxy_pass http://127.0.0.1:8080;
+
+        proxy_http_version 1.1;
+
+        # WebSocket 升级（远程桌面走 /remoter/ws，不配这两行连不上）
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+
+        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;
+
+        # 远程桌面连接长时间空闲，避免默认 60s 被 nginx 掐断
+        proxy_read_timeout 3600s;
+        proxy_send_timeout 3600s;
+
+        # 大文件/流式传输时避免缓冲占内存（可选）
+        # proxy_buffering off;
+    }
+}
+
+# ============================================================
+#  方案A（根路径部署）：不设 YAMA_WEB_BASE_PATH，用下面这段替代上面
+# ============================================================
+# server {
+#     listen 443 ssl http2;
+#     server_name 你的域名.com;
+#     ssl_certificate     /etc/letsencrypt/live/你的域名.com/fullchain.pem;
+#     ssl_certificate_key /etc/letsencrypt/live/你的域名.com/privkey.pem;
+#
+#     location / {
+#         proxy_pass http://127.0.0.1:8080;
+#         proxy_http_version 1.1;
+#         proxy_set_header Upgrade $http_upgrade;
+#         proxy_set_header Connection "upgrade";
+#         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 3600s;
+#         proxy_send_timeout 3600s;
+#     }
+# }