feat(voice): WhatsApp Cloud Calling — UI [6] (#14346)

## Summary

Frontend for WhatsApp Cloud Calling: header / contact-panel call
buttons, ringing widget, accept/reject/hangup, mute, in-bubble audio
player + transcript, recording-on-hangup upload, mid-call reload
warning. WebRTC is browser-direct to Meta — no media server bridge.

## Closes
- https://linear.app/chatwoot/issue/PLA-150

## How to test

Requires backend support — the controller, services, model changes, and
routes ship in **#14334** (`feature/pla-150`). Merge / deploy that first
(or simultaneously); the FE alone won't function without those
endpoints.

Then on staging, for a WhatsApp Cloud + embedded-signup inbox with the
new \`Configuration → Enable voice calling\` toggle ON and webhook
registered:

1. **Outbound** — open a conversation, click the phone icon in the
conversation header (or contact panel), grant mic, your phone rings,
answer, audio both ways, hang up. Recording + transcript land in the
bubble within ~10s.
2. **Inbound** — call the business number from your phone. The
FloatingCallWidget appears bottom-right with caller name. Click accept,
audio both ways, hang up. Recording + transcript appear.
3. **Mute** — during an active WhatsApp call, click the mic icon next to
hangup. Speech stops reaching Meta until you click again.
4. **Mid-call reload guard** — try `Cmd-R` during an active call;
browser shows a confirm prompt.

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

enterprise/app/controllers/api/v1/accounts/conference_controller.rb

@@ -27,7 +27,10 @@ class Api::V1::Accounts::ConferenceController < Api::V1::Accounts::BaseControlle
 
   def destroy
     call = resolve_call!
+    rejecting = agent_rejecting_before_pickup?(call)
+    # Tear down provider side first so a teardown failure leaves the call repairable.
     Voice::Provider::Twilio::ConferenceService.new(call: call).end_conference
+    finalize_as_agent_reject!(call) if rejecting
     render json: { status: 'success', id: call.conversation.display_id }
   end
 
@@ -59,4 +62,21 @@ class Api::V1::Accounts::ConferenceController < Api::V1::Accounts::BaseControlle
   def render_call_already_accepted(error)
     render json: { error: error.message }, status: :conflict
   end
+
+  # A hangup before pickup is treated as an agent rejection, matching WhatsApp.
+  def agent_rejecting_before_pickup?(call)
+    call.ringing? && call.accepted_by_agent_id.nil?
+  end
+
+  def finalize_as_agent_reject!(call)
+    # Re-check under a row lock: a webhook may have accepted/completed the call
+    # while end_conference was in flight, so don't force agent_rejected on stale state.
+    rejected = call.with_lock do
+      next false unless agent_rejecting_before_pickup?(call)
+
+      call.update!(status: 'failed', end_reason: 'agent_rejected', accepted_by_agent_id: Current.user.id)
+      true
+    end
+    Voice::CallMessageBuilder.new(call).update_status!(status: 'failed', agent: Current.user) if rejected
+  end
 end