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。

platform_web/api/contracts.md

@@ -24,7 +24,7 @@ Normal browser login uses the platform's HttpOnly SameSite cookie and `credentia
 
 - `createServerWorkflow` posts `ServerLifecycleCreateRequest` with the create-wizard deployment definition to `/server-instances/workflows/create`, including deployment mode, plugin create inputs, and custom startup fields when provided. It never includes a deployment target, Run endpoint, lifecycle profile, or Run identity binding. The generated Run package uses plugin defaults and Platform observes the active Run from its authenticated heartbeat.
 - `getServerRuntimeBinding` reads `/server-instances/{id}/runtime-binding`; `updateServerRuntimeBinding` patches the selected profile and logical refs for internal/advanced logical transports. Server detail must not expose a manual runtime-binding tab or require these fields before normal start/stop when plugin-declared deployment/lifecycle data is sufficient. Responses contain only profile metadata, logical key names, configured/secret-backed flags, missing keys, and safe reasons. They never contain stored refs or secret values.
-- `startServerInstance` and `stopServerInstance` post `ServerLifecycleCommandRequest` with the current config version and receive the lifecycle job response.
+- `startServerInstance`, `stopServerInstance`, `restartServerInstance`, and `updateServerGame` post `ServerLifecycleCommandRequest` with the current config version and receive the lifecycle job response. `restart` queues the plugin-declared stop action before the matching start action, and `update` queues the plugin-declared install/update action, which closes a running server gracefully before the game files change.
 - `listServerAdministratorCandidates`, `addServerAdministrator`, and `removeServerAdministrator` call server membership endpoints so server owners can invite or remove active non-platform-admin server administrators.
 - Game-specific pages use the scoped `plugin-data` collection API and declared plugin bridge machine actions; Platform does not expose game-specific projection or workflow clients.
 - `dispatchFileOperation` posts `FileOperationDispatchRequest` to `/file-operations/dispatch` using logical file keys and scoped refs rather than raw host paths; it remains the low-level compatibility dispatch for file work.