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).

package-lock.json

@@ -21,7 +21,7 @@
         "puppeteer-core": "^23.11.1"
       },
       "engines": {
-        "node": ">=18"
+        "node": ">=22"
       }
     },
     "node_modules/@pixi-spine/base": {