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/web/index.html

@@ -10,9 +10,9 @@
     <meta name="apple-mobile-web-app-title" content="Remoter">
     <meta name="mobile-web-app-capable" content="yes">
     <meta name="theme-color" content="#1a1a2e">
-    <link rel="manifest" href="/manifest.json">
+    <link rel="manifest" href="__BASE_PATH__/manifest.json">
     <!-- xterm.js (远程终端). Files served by WebService from RC binary resources. -->
-    <link rel="stylesheet" href="/static/xterm.css">
+    <link rel="stylesheet" href="__BASE_PATH__/static/xterm.css">
     <link rel="icon" type="image/png" href="data:image/png;base64,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">
     <style>
         * { margin: 0; padding: 0; box-sizing: border-box; }
@@ -1349,8 +1349,8 @@
         </div>
     </div>
 
-    <script src="/static/xterm.js"></script>
-    <script src="/static/xterm-fit.js"></script>
+    <script src="__BASE_PATH__/static/xterm.js"></script>
+    <script src="__BASE_PATH__/static/xterm-fit.js"></script>
 
     <!-- Opus codec for audio decompression -->
     <script src="https://cdn.jsdelivr.net/npm/opus.js@0.5.0/dist/opus.js"></script>
@@ -1524,7 +1524,7 @@
             const protocol = location.protocol === 'https:' ? 'wss:' : 'ws:';
             updateWsStatus('connecting');
             try {
-                ws = new WebSocket(protocol + '//' + location.host + '/ws');
+                ws = new WebSocket(protocol + '//' + location.host + '__BASE_PATH__/ws');
             } catch (e) {
                 updateWsStatus('disconnected');
                 scheduleReconnect();