Parent controls for children, name-tile sign-in, restricted Learn search, simple mode

- Sign-in page shows name tiles on remembered devices; tap a name, then PIN or passkey
- Music and Movies are separate on the server; Plex can be locked to a child's managed profile
- Activity log, weekly summary and alerts to parents; per-area and weekend limits
- Requests from children (Ask button) answered in Settings; bonus screen time from rewards
- Restricted Learn search (Simple English Wikipedia, blocked words) replaces web search for children
- Simple mode (big-button home) for young children or grandparents
- Child usage kept in memory instead of read from disk on every request
- Tests and README updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/video.js

@@ -226,6 +226,7 @@ async function videoWatch(id) {
   videoStop();
   try { pl.a.pause(); } catch {}
   if (!vdHooked) { vdHooked = true; pl.a.addEventListener('play', () => { if (vp) videoStop(); }); } // one thing at a time: music starting ends the video
+  if (typeof actLog === 'function') actLog('watch', (m.grandparentTitle ? m.grandparentTitle + ': ' : '') + (m.title || ''));
   const media = m.Media[0], part = media.Part[0], streams = part.Stream || [], fromStart = store.get('video_from_start') === id;
   if (fromStart) store.del('video_from_start');
   const el = document.createElement('video'); el.playsInline = true; el.autoplay = true; el.id = 'vv';