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).

tools/doctor.mjs

@@ -164,7 +164,7 @@ async function main() {
 
   section('运行环境');
   const node = checkNode();
-  row(node.ok ? (node.recommended ? 'ok' : 'warn') : 'err', 'Node.js', `v${node.version}` + (node.ok ? (node.recommended ? '' : '（推荐 22 LTS）') : `（需要 ≥ ${MIN_NODE}：https://nodejs.org/zh-cn/download）`));
+  row(node.ok ? (node.recommended ? 'ok' : 'warn') : 'err', 'Node.js', `v${node.version}` + (node.ok ? (node.recommended ? '' : '（推荐 22 / 24 LTS）') : `（需要 ≥ ${MIN_NODE}：https://nodejs.org/zh-cn/download）`));
   const npmV = tool(IS_WIN ? 'npm.cmd' : 'npm', ['--version']);
   row(npmV ? 'ok' : 'warn', 'npm', npmV ? `v${npmV}` : '未找到（安装 Node.js 时会自带）');