Family devices: shared-screen family board with a who-is-this profile picker

- Admin can make a screen a family device; it opens on a family board
- Name tiles with KID labels; kids tap, others enter a PIN (lockout after 5 wrong tries)
- Name label with Switch user, auto-return to the board after 5 idle minutes
- Short 30-minute sessions on family devices
- Settings section for PIN and turning a device on or off
- Test, README and roadmap updated

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

public/boot.js

@@ -18,7 +18,7 @@
   setInterval(checkForUpdate, 10 * 60e3);
   await loadMe();
   await loadSettings();
-  sgStart(); if (typeof chStart === 'function') chStart(); if (typeof kidStart === 'function') kidStart();
+  sgStart(); if (typeof chStart === 'function') chStart(); if (typeof kidStart === 'function') kidStart(); if (typeof devStart === 'function') devStart();
   addEventListener('hashchange', route);
   restorePlayer();
   route();