feat(presence): live stream badges, honest ring delivery, cross-signal DMs

- Camera and screen-share badges are decided by `shouldShowStreamIndicator`,
  so a live stream is visible from outside the voice channel and clicking the
  badge joins the streamer's channel before focusing the stream.
- `ringParticipants` reports whether a `direct-call` ring reached anyone; a
  call that reached nobody shows `call.errors.ringUndelivered` instead of
  sitting in "calling" as if it were live.
- Direct messages resolve every local identity alias, so a conversation
  opened from a foreign roster entry lands in the same thread.

toju-app/public/i18n/catalog/call.json

@@ -49,7 +49,8 @@
       "microphonePermissionDenied": "Microphone access is blocked. Allow the microphone permission in system settings to join calls.",
       "microphoneUnavailable": "Could not start the microphone. Close other apps that use it and try again.",
       "cameraPermissionDenied": "Camera access is blocked. Allow the camera permission in system settings to share video.",
-      "cameraUnavailable": "Could not start the camera. Close other apps that use it and try again."
+      "cameraUnavailable": "Could not start the camera. Close other apps that use it and try again.",
+      "ringUndelivered": "Could not reach anyone in this call. They may be offline or on another server."
     }
   }
 }