Node 22+ everywhere, LF text on Windows checkouts, CI actions v7

- Node minimum is 22 in package.json engines, the start scripts, the service installer, setup and doctor,
  matching the README, the release notes and the CI matrix (22 / 24).
- .gitattributes: CSS, HTML, JSON, Markdown and YAML check out with LF, so `node --test` on Windows matches the
  CSS rules the UI tests read; the Windows test step is no longer continue-on-error.
- CI: actions/checkout@v7 and actions/setup-node@v7 (Node 24 runtime).

scripts/install-service-windows.ps1

@@ -118,7 +118,7 @@ try {
   if (-not $nodeCmd) { throw '未找到 Node.js：请先安装（winget install OpenJS.NodeJS.LTS），然后重新打开 PowerShell。' }
   $nodeExe = $nodeCmd.Source
   $major = [int](((& $nodeExe -v) -replace '^v', '').Split('.')[0])
-  if ($major -lt 18) { throw "Node.js 版本太旧（需要 18+）：$(& $nodeExe -v)" }
+  if ($major -lt 22) { throw "Node.js 版本太旧（需要 22+）：$(& $nodeExe -v)" }
   if ($nodeExe -like "$env:USERPROFILE*") {
     Write-Host "注意：node.exe 位于用户目录（$nodeExe，nvm/便携版？）。SYSTEM 账户一般也能运行它；若服务起不来，请改用 winget / 官网安装包安装的 Node.js。" -ForegroundColor Yellow
   }