Back up unsaved editor work locally, structure the settings, fix archive accessibility

- The editor keeps unsaved changes in the browser and offers them
  after a crash, a closed tab or an expired session. No timed save on
  the server: every save is a full revision.
- The save status stays visible in narrow windows.
- Settings get a sticky section bar, two folded groups and a save bar
  that stays in view.
- The admin post list fetches terms and images once, not per post.
- Archive post titles are second-level headings, the archive head
  keeps full text contrast, the skip link sits above a sticky header,
  a linked image without alternative text names its link.
- The editor check starts through the dev router like the others.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

scripts/editor-check.mjs

@@ -14,7 +14,7 @@ await new Promise(resolve => probe.listen(0, '127.0.0.1', resolve));
 const port = probe.address().port;
 await new Promise(resolve => probe.close(resolve));
 const origin = `http://127.0.0.1:${port}`;
-const server = spawn(php, ['-d', 'upload_max_filesize=8M', '-d', 'post_max_size=10M', '-d', 'memory_limit=256M', '-S', `127.0.0.1:${port}`, '-t', 'public'], {
+const server = spawn(php, ['-d', 'upload_max_filesize=8M', '-d', 'post_max_size=10M', '-d', 'memory_limit=256M', '-S', `127.0.0.1:${port}`, '-t', 'public', 'bin/dev-router.php'], {
   windowsHide: true,
   env: { ...process.env, APP_ENV: 'prod', APP_DEBUG: '0', APP_SECRET: randomBytes(32).toString('hex'), DATABASE_URL: fixture.databaseUrl, MEDIA_DIRECTORY: fixture.mediaDirectory, MEDIA_MIRROR_DIRECTORY: fixture.mediaDirectory + '-abbild', SITE_ORIGIN: origin },
   stdio: 'ignore',