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/start-windows.ps1

@@ -31,7 +31,7 @@ function Test-Node {
 
 $node = Test-Node
 if (-not $node) {
-  Write-Host '未找到 Node.js（需要 18 或更高，推荐 22 LTS）。' -ForegroundColor Yellow
+  Write-Host '未找到 Node.js（需要 22 或更高，22 / 24 LTS）。' -ForegroundColor Yellow
   $winget = Get-Command winget -ErrorAction SilentlyContinue
   if ($winget) {
     Write-Host '可以用 Windows 自带的 winget 安装：  winget install OpenJS.NodeJS.LTS'
@@ -49,8 +49,8 @@ if (-not $node) {
     Pause-Exit 1
   }
 }
-if ($node.Major -lt 18) {
-  Write-Host "Node.js $($node.Version) 太旧，需要 18 或更高：winget upgrade OpenJS.NodeJS.LTS  或  https://nodejs.org/zh-cn/download" -ForegroundColor Red
+if ($node.Major -lt 22) {
+  Write-Host "Node.js $($node.Version) 太旧，需要 22 或更高：winget upgrade OpenJS.NodeJS.LTS  或  https://nodejs.org/zh-cn/download" -ForegroundColor Red
   Pause-Exit 1
 }