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/reader.js

@@ -232,6 +232,7 @@ async function rdOpen(id) {
     notes = await rdApi('/book/' + id + '/notes');
   } catch (e) { if (!location.hash.startsWith('#/read')) return; document.body.classList.remove('editing'); v.innerHTML = `<div class="wrap"><a class="btn ghost" href="#/read">${icon('back')}Books</a><p class="err">${esc(e.message)}</p></div>`; return; }
   if (!location.hash.startsWith('#/read/open')) return;
+  if (typeof actLog === 'function') actLog('read', book.title || 'A book');
   new RdReader(book, notes).start();
 }