feat: 支持离线运行时（runtime 目录）+ 动态生成自启 vbs

- FindNodeExe/FindDshBinJs/FindNpmCli：标准安装或应用旁 runtime 目录均可
- WriteServiceVbs 按当前环境动态生成（跨设备路径正确），启动时刷新
- 为离线安装包（Node 便携 + dsh 依赖内置）做准备

app/start-dsh-service.vbs

@@ -1,4 +1,3 @@
-' Start dsh (DeepSeek Harness) service in background, no window.
-' Used by "autostart" tray option (registry Run entry via wscript).
+' Start dsh service (hidden, auto-generated)
 Set ws = CreateObject("WScript.Shell")
 ws.Run "cmd /c """"C:\Program Files\nodejs\node.exe"" ""C:\Users\VanuSystems-Mu\AppData\Roaming\npm\node_modules\@deepseek-ai\dsh\lib\bin.js"" web > ""C:\Users\VanuSystems-Mu\AppData\Local\DeepSeekHarness\app\web.log"" 2>&1""", 0, False