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>

public/sw.js

@@ -1,5 +1,5 @@
 // App-shell cache only; Seafile/API traffic always goes to the network.
-const CACHE = 'hub-v58';
+const CACHE = 'hub-v59';
 const SHARE = 'hub-share'; // files shared into the app from other apps, held until the person picks a folder
 const SHELL = ['/icon.svg', '/manifest.webmanifest', '/icons/icon-192.png', '/icons/apple-touch-icon.png'];