admin: System page with restart steps, Record calls on the Calling tab

System shows whether telephony runs and needs a restart, and how to restart it
(docker compose restart asterisk); the dashboard's restart warning, the Network hint and
the public IP email point there. The user drawer's Calling tab gets the Record calls
select the spec listed (recordMode, already in the dialplan). e2e m11-system.mjs.

Task: M11-T7

docs/admin-guide/troubleshooting.md

@@ -128,7 +128,8 @@ nobody is on a call:
 docker compose restart asterisk
 ```
 
-The banner goes away a few seconds after Asterisk is back.
+The admin page **System** shows the same command. It says "Restart: Not needed" and the banner
+goes away a few seconds after Asterisk is back.
 
 ## Locked out