feat: 服务器列表加「文件」按钮直达文件管理

- servers.html: renderActions 加「文件」链接(琥珀色) → /app/files.html?server_id=X
- files.html: 支持 server_id URL参数, 自动选中服务器并浏览 /www/wwwroot

web/app/files.html

@@ -705,6 +705,15 @@
     // Enter key in path input
     document.getElementById('dirPath').addEventListener('keydown',e=>{if(e.key==='Enter')browseDir()});
 
-    loadServers();
+    // Auto-select server from URL param (e.g., from servers.html "文件" button)
+    loadServers().then(()=>{
+      const urlServerId=new URLSearchParams(window.location.search).get('server_id');
+      if(urlServerId){
+        const sel=document.getElementById('serverSelect');
+        sel.value=urlServerId;
+        _currentServerId=parseInt(urlServerId);
+        browseDir('/www/wwwroot');
+      }
+    });
   </script>
 </body></html>

web/app/servers.html

@@ -359,6 +359,7 @@
 
     function renderActions(s){
       let html=`<a href="/app/terminal.html?server_id=${s.id}" onclick="event.stopPropagation()" class="text-brand-light hover:underline text-xs mr-2">终端</a>`;
+      html+=`<a href="/app/files.html?server_id=${s.id}" onclick="event.stopPropagation()" class="text-amber-400 hover:underline text-xs mr-2">文件</a>`;
       if(s.agent_version) html+=`<button onclick="event.stopPropagation();_quickCheck(${s.id})" class="text-emerald-400 hover:underline text-xs mr-2">检查</button>`;
       html+=`<button onclick="event.stopPropagation();showEditServer(${s.id})" class="text-slate-400 hover:underline text-xs mr-2">编辑</button>`;
       html+=`<button onclick="event.stopPropagation();deleteServer(${s.id})" class="text-red-400 hover:underline text-xs">删除</button>`;