Family Chat (2.0): a built-in messenger for the family, phase 1

- Chat tab: direct chats and groups, text, attachments, replies, reactions, edit and delete, unread counts, search, drafts, mute and archive
- Live delivery over server-sent events; phone push for people who are not in the app (muted chats stay quiet)
- chat.js keeps conversations and files in data/chat; push.notify sends one person a notification
- Roadmap updated: phase 1 done, combined inbox with Signal still to do

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

README.md

@@ -180,3 +180,5 @@ Files are kept in the data folder under `mystore/` (up to 1 GB each; extensions
 
 **iPad and Screen Time:** Settings, Admin, *iPad and Screen Time* explains the simple setup (Screen Time, Content Restrictions, Web Content: **Limit Adult Websites**, and add only the hub's address under *Always Allow*), lists the web addresses the app needs (the hub, plus the document editor for the Office tab) for anyone using **Allowed Websites Only**, shows other addresses devices were actually seen reaching, and has a *Check this device* button to run on the iPad. The hub sends a report-only Content-Security-Policy (nothing is blocked) so devices report any other address a page loads, and pictures from other sites (podcast search covers, Plex Home pictures, a Verse By Verse cover, search answers) are passed through the hub (`/api/img`) so the browser only talks to the hub for them. Extensions and Sites you add may still reach their own addresses. If the document editor is put behind the same address as the hub (a reverse proxy path), even that one drops off the list.
 
+**Chat** (turn it on per person in the admin screen): the family's own messenger, with the same look as the Signal tab. Direct chats and groups between people who have an account here, text with links and emoji, attachments (up to 100 MB each; pictures, audio and video show in the chat), replies, reactions, edit and delete for everyone, unread counts on the menu and the tab title, search (chats and messages), drafts that survive closing the app, mute and archive, live delivery while the app is open and a phone push when it is not (the same notification devices as reminders, and muted chats stay quiet). Messages and files are kept readable on this server in `data/chat`; end-to-end encryption is not built. Planned next: read ticks, typing, disappearing messages, mentions, pins, voice notes, link previews, polls (see `docs/v2-roadmap.md`).
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