feat(voice): Wire Twilio voice flow through unified call model (#14091)

Twilio voice now uses first-class `Call` records as the source of truth
for call state, instead of storing it on
`conversation.additional_attributes` and `conversation.identifier`. Each
call gets its own record, its own `voice_call` bubble matched by
`call_sid`, and its own conference name keyed off `Call.id`. Multiple
calls on the same conversation (for `lock_to_single_conversation`
inboxes) now work correctly, and the conversation card stays in sync
with the real latest message.
Fixes https://linear.app/chatwoot/issue/PLA-121/lock-to-single-thread

---------

Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>

app/javascript/dashboard/composables/useCallSession.js

@@ -42,8 +42,8 @@ export function useCallSession() {
     );
   });
 
-  const endCall = async ({ conversationId, inboxId }) => {
-    await VoiceAPI.leaveConference(inboxId, conversationId);
+  const endCall = async ({ conversationId, inboxId, callSid }) => {
+    await VoiceAPI.leaveConference({ inboxId, conversationId, callSid });
     TwilioVoiceClient.endClientCall();
     durationTimer.stop();
     callsStore.clearActiveCall();
@@ -66,6 +66,7 @@ export function useCallSession() {
       await TwilioVoiceClient.joinClientCall({
         to: joinResponse?.conference_sid,
         conversationId,
+        callSid,
       });
 
       callsStore.setCallActive(callSid);