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/player.js

@@ -68,6 +68,7 @@ function loadCur(delay = 220) {
     if (tok !== loadTok) return;
     const hit = tc.m.get(t.src);
     pl.a.src = hit && !pl.alt.has(t.key) ? hit.url : srcOf(t);
+    if (typeof actLog === 'function') actLog(/podcast|audiobook|\/ab\/|radio/.test(String(t.src || '')) ? 'listen' : 'play', (t.artist ? t.artist + ' - ' : '') + (t.title || ''));
     pl.a.play().catch(e => { if (e && e.name === 'NotAllowedError') { pl.buf = false; syncUI(); toast('Tap play to start'); } });
     tcKick();
     const n = pl.q[pl.i + 1]; if (n) new Image().src = px.art(n.thumb, 600);