Add graceful SCUM stop, restart, and version update flow

SCUM 停止/重启/更新以前只有“结束进程”这一条路，插件没有声明任何优雅关闭方式，
平台也没有把停止后重新启动串起来。现在插件声明自己的关闭脚本，run 先执行它，
平台在停止或更新成功后再自动拉起服务。

run:
- lifecycle stop 支持插件声明的 gracefulStop（可执行文件、参数、环境、超时、
  fallback=report|terminate）；关闭命令超时且声明 report 时任务失败，不再默默杀进程。
- 新增 steam.update 依赖探针：调用 steamcmd +app_info_print 获取公开分支 buildid，
  与本地 steamapps/appmanifest_<appid>.acf 的 buildid 比较，输出
  installed/latest/update=yes|no|unknown。

platform:
- 新增 POST /api/v1/server-instances/{id}/restart 与 /update。
- restart 派发插件 stop 动作（走优雅关闭），终态成功后入队 start 作业。
- update 派发插件 install 动作；插件在更新前必须先优雅关闭 SCUM，关闭失败直接拒绝
  SteamCMD 更新，成功后平台再拉起服务。
- 依赖检查输入带上插件声明的服务器安装根目录，供 steam.update 读取 appmanifest。

plugin (SCUM server plugin 0.1.16):
- bin/scum-stop.cmd：解析已声明的可执行文件路径，定位同路径正在运行的 SCUMServer.exe，
  通过本地 RCON 公告并发送关闭命令，等待进程自行退出；不再使用 taskkill。
- bin/scum-rcon.ps1：插件自有的 Source RCON 客户端，从 UE4SS mod config.ini 读取
  密码/端口，密钥不离开本机。
- actions/stop.json 声明 gracefulStop；actions/install.json 更新前先执行同一关闭脚本。

platform_web:
- 服务器详情新增“重启”按钮和“SCUM 版本更新”面板；点“检查更新”查询公开分支版本，
  只有检测到更新时“更新版本”按钮才会置为可用并高亮，点击后先确认再派发更新任务。

plugins/scripts/validate-manifest.ts

@@ -223,6 +223,15 @@ export function validateLifecycleActionFile(actionPath: string, expectedAction?:
   if ((declaration.action === "stop" || declaration.action === "status") && declaration.mode !== "control") {
     errors.push(`lifecycleAction.mode: ${declaration.action} must be control`);
   }
+  const gracefulStop = (action as { gracefulStop?: { executableKey?: unknown } }).gracefulStop;
+  if (gracefulStop !== undefined) {
+    if (declaration.action !== "stop") {
+      errors.push("lifecycleAction.gracefulStop: only the stop action may declare a graceful stop step");
+    }
+    if (typeof gracefulStop.executableKey !== "string") {
+      errors.push("lifecycleAction.gracefulStop.executableKey: required for a declared graceful stop step");
+    }
+  }
   return errors;
 }
 
@@ -754,6 +763,11 @@ export function validateManifestFile(manifestPath: string): string[] {
     if (typeof executableKey === "string" && !assetValidation.declared.has(executableKey)) {
       errors.push(`lifecycleAction.${declaration.action}.executableKey: ${executableKey} must be declared in manifest.assetFiles`);
     }
+    const gracefulStop = typeof action === "object" && action !== null ? (action as { gracefulStop?: { executableKey?: unknown } }).gracefulStop : undefined;
+    const gracefulExecutableKey = gracefulStop && typeof gracefulStop.executableKey === "string" ? gracefulStop.executableKey : undefined;
+    if (gracefulExecutableKey && !assetValidation.declared.has(gracefulExecutableKey)) {
+      errors.push(`lifecycleAction.${declaration.action}.gracefulStop.executableKey: ${gracefulExecutableKey} must be declared in manifest.assetFiles`);
+    }
   }
 
   if (typeof manifest === "object" && manifest !== null && "server" in manifest) {