fix(voice): keep ringing WhatsApp calls alive across page refresh

Inverted the previous decision: only the active (accepted) call gets
terminated on pagehide, since its WebRTC session dies with the page and
genuinely can't be rejoined. Ringing calls have no WebRTC state yet —
they're just a row on the backend and a state on Meta — so killing them
on refresh would needlessly hang up on the customer when the agent
intended to recover their UI, not reject the call.

After this, the flow on refresh during a ringing inbound is:
  - beforeunload prompt fires (warning the agent)
  - pagehide does nothing for ringing calls; active calls still terminate
  - new page loads, conversation messages fetch
  - seedCallsFromHydratedMessages picks up status='ringing' voice_call
    messages and populates the calls store
  - FloatingCallWidget reappears with Accept; agent clicks; acceptIncomingCall
    fetches the SDP via /whatsapp_calls/:id and the call connects

app/javascript/dashboard/composables/useCallSession.js

@@ -6,7 +6,6 @@ import { useCallsStore } from 'dashboard/stores/calls';
 import {
   useWhatsappCallSession,
   sendWhatsappTerminateBeacon,
-  sendWhatsappCallBeacon,
   cleanupWhatsappSession,
 } from 'dashboard/composables/useWhatsappCallSession';
 import { handleVoiceCallCreated } from 'dashboard/helper/voice';
@@ -70,15 +69,13 @@ export function useCallSession() {
     });
   };
 
-  // pagehide fires after the user confirms the prompt. Beacon a terminate for
-  // every WhatsApp call in the store — active OR ringing — since browser-direct
-  // WebRTC has no rejoin path, so any call that survives the close becomes
-  // permanently orphaned on Meta's side.
+  // pagehide fires after the user confirms the refresh prompt. Terminate the
+  // active call only — its WebRTC session dies with the page and can't be
+  // rejoined. Ringing calls intentionally stay alive on Meta so the agent can
+  // pick them up after the page reloads (FloatingCallWidget rehydrates them
+  // via seedCallsFromHydratedMessages once the conversation messages land).
   const handlePageHide = () => {
     sendWhatsappTerminateBeacon();
-    callsStore.calls
-      .filter(c => c.provider === 'whatsapp' && !c.isActive && c.callId)
-      .forEach(c => sendWhatsappCallBeacon(c.callId));
   };
 
   const handleTwilioDisconnected = () => callsStore.clearActiveCall();