Signal: keep messages that arrive glued together, one chat per person, receipts by time, faster reconnect; edit contacts, clear and remove chats; debug list

- read every JSON value in a frame (lines, arrays), binary frames too
- a person seen by number and by private id is one conversation (merged)
- delivery/read receipts match on message time, not on who sent them
- reconnect every 1-5 s; the chat list says when the link was down
- /api/signal/debug: kinds of messages seen lately (no text)
- edit a contact (kept in the app and sent to Signal), clear messages, remove a chat; right-click menu in the list; name for a new number
- tests: 54 checks

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

README.md

@@ -59,7 +59,8 @@ e.g. hub.necloud.us. Settings: `SEAFILE_URL`, `ONLYOFFICE_URL` env vars in docke
   (if you switch it on in Settings -> Signal alerts) a desktop notification when the app is in the background; sound and notifications are saved per device. It talks to your account through the community `signal-cli-rest-api` bridge, which is one more *linked device* of your account
   (like Signal Desktop; not an official Signal product). The `signal` container in `docker-compose.yml` runs it; remove that service and the hub's `SIGNAL_API_URL` line to skip Signal.
   First time: open the Signal tab, then on your phone Signal -> Settings -> Linked devices -> Link new device and scan the code. You can send and receive text, photos,
-  files, voice messages (played, not recorded), replies, reactions, groups and read receipts; there are no calls. Only messages from after linking appear (Signal does
+  files, voice messages (played, not recorded), replies, reactions, groups and read receipts; there are no calls. In a chat, the ... button edits the contact (the name you give is shown in the app and sent to Signal),
+  clears the messages, or removes the chat from the app (it stays on your phone, and a new message starts it again); right-click a chat in the list for the same menu. A diagnostic list of what arrived lately (kinds only, no message text) is at `/api/signal/debug`. Only messages from after linking appear (Signal does
   not copy older ones to a new device) and they are kept in `/data/signal`. The link keys live in the `nehub-signal` volume (a Docker *volume*, not a host folder: the bridge runs as user 1000 and a root-owned host folder gives "permission denied"; if you do want a folder, `chown -R 1000:1000` it first): whoever gets into your server can read your chats,
   so only give the **Signal** tab to people you would trust with your Signal (it is one shared account, admins always have it). Signal drops a linked device that is
   not connected for about a month; the hub stays connected, so this only matters if the stack is switched off.