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>

README.md

@@ -196,5 +196,7 @@ Files are kept in the data folder under `mystore/` (up to 1 GB each; extensions
 
 **Notifications** (the bell on Home and Family): a list of what you have not seen yet: chat messages (one line per conversation, with a count), reminders for tasks, events and mail, and family announcements. Tap one to open it; mark all read or clear. Kept per person in `inbox.json`.
 
+**Family devices** (Settings, under Passkeys): for a kitchen tablet or the family computer. An admin turns on *Make this a family device* while signed in on it; from then on it opens on the **family board** (announcement, today's family calendar, chores with progress, shopping list, family tasks and notes) and a row of name tiles, children marked **KID**. Tap your name: a child signs in with one tap, everyone else enters a PIN they set in Settings (five wrong tries lock that person for five minutes; there is also a passkey link). A label with your name and **Switch user** stays on screen, and the device goes back to the board after five idle minutes (music playing keeps it signed in). Sessions on a family device last 30 minutes at a time, not months. Turn it off from the same place. The Family calendar and Family task list are shared by everyone and appear on the board.
+
 On a tablet or with the menu collapsed, the menu rail shows icons only (the name appears on hover) when the window is not tall enough for a label under every icon.