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/style.css

@@ -1057,3 +1057,6 @@ body.vizopen { overflow: hidden; }
 .inboxbell { position: relative; }
 .inboxbell .nbadge { position: absolute; top: -6px; right: -6px; }
 .fmrow .grow { min-width: 0; }
+
+#devchip { position: fixed; top: calc(env(safe-area-inset-top, 0px) + 8px); right: 10px; z-index: 60; display: flex; align-items: center; gap: 8px; background: var(--panel); border: 1px solid var(--line); border-radius: 22px; padding: 4px 4px 4px 14px; box-shadow: 0 4px 14px rgba(0,0,0,.3); }
+#devchip .btn { min-height: 34px; padding: 0 14px; border-radius: 18px; } .devwho { display: flex; align-items: center; gap: 6px; } .devkid { font-style: normal; background: #2f9e6e; color: #fff; border-radius: 8px; padding: 1px 7px; font-size: 11px; font-weight: 700; }