fix(voice): align outbound WhatsApp call lifecycle with real pickup

A pile of related fixes around the dashboard's WhatsApp call flow:

- ConversationHeader / Contacts/VoiceCallButton: drop the immediate
  setCallActive at initiate time. The call sits in incomingCalls
  (callDirection: outbound) until the backend signals real pickup, so
  the duration timer never starts pre-pickup. Phone button is disabled
  whenever there is an active or incoming call.

- FloatingCallWidget:
  * Loop a ringtone (bell.mp3) for inbound ringing only.
  * Hide the green Join button for outbound — the agent has nothing to
    "join", and clicking it routed through acceptIncomingCall →
    prepareInboundAnswer → cleanup() and tore down the live outbound
    session before the API 409 ("already accepted by another agent").
  * Auto-join watcher skips whatsapp outbound (Twilio's joinConference
    flow only).

- useCallSession:
  * joinCall short-circuits for outbound calls — defense-in-depth so
    no future surface can re-trigger the destroyed-session bug.
  * endCall + outbound rejectIncomingCall pass call.callId to
    endActiveCall, so terminate fires even if module state was wiped.

- useWhatsappCallSession:
  * New recorderArmed flag, reset by cleanup. ontrack only calls
    setupRecorder when armed.
  * Inbound's acceptIncomingCall arms the recorder before the API
    round-trip (agent click = pickup).
  * armOutboundRecorder exported for the cable handler when ACCEPTED
    arrives.
  * endActiveCall accepts a callIdOverride to fall back when the
    module's activeCallId was nulled by an earlier cleanup.

- actionCable:
  * Split the cable contract: outbound_connected only applies the SDP
    answer (tunnel-up signal); outbound_accepted (new) is the real
    pickup signal — flips active and arms the recorder.

app/javascript/dashboard/components-next/Contacts/VoiceCallButton.vue

@@ -93,6 +93,8 @@ const startWhatsappCall = async inboxId => {
   }
 
   const callsStore = useCallsStore();
+  // Stay non-active until the connect cable event arrives — flipping to active
+  // here would start the duration timer before the contact picks up.
   callsStore.addCall({
     callSid: response.call_id,
     callId: response.id,
@@ -101,7 +103,6 @@ const startWhatsappCall = async inboxId => {
     callDirection: 'outbound',
     provider: 'whatsapp',
   });
-  callsStore.setCallActive(response.call_id);
 
   useAlert(t('CONTACT_PANEL.CALL_INITIATED'));
   navigateToConversation(conversationId);