feat(voice): Incoming voice calls [EE] (#12361)

This PR delivers the first slice of the voice channel: inbound call
handling. When a customer calls a configured voice
number, Chatwoot now creates a new conversation and shows a dedicated
call bubble in the UI. As the call progresses
(ringing, answered, completed), its status updates in real time in both
the conversation list and the call bubble, so
agents can instantly see what’s happening. This focuses on the inbound
flow and is part of breaking the larger voice
feature into smaller, functional, and testable units; further
enhancements will follow in subsequent PRs.

references: #11602 , #11481  

## Testing

- Configure a Voice inbox in Chatwoot with your Twilio number.
- Place a call to that number.
- Verify a new conversation appears in the Voice inbox for the call.
- Open it and confirm a dedicated voice call message bubble is shown.
- Watch status update live (ringing/answered); hang up and see it change
to completed in both the bubble and conversation
list.
- to test missed call status, make sure to hangup the call before the
please wait while we connect you to an agent message plays


## Screens

<img width="400" alt="Screenshot 2025-09-03 at 3 11 25 PM"
src="https://github.com/user-attachments/assets/d6a1d2ff-2ded-47b7-9144-a9d898beb380"
/>

<img width="700" alt="Screenshot 2025-09-03 at 3 11 33 PM"
src="https://github.com/user-attachments/assets/c25e6a1e-a885-47f7-b3d7-c3e15eef18c7"
/>

<img width="700" alt="Screenshot 2025-09-03 at 3 11 57 PM"
src="https://github.com/user-attachments/assets/29e7366d-b1d4-4add-a062-4646d2bff435"
/>



<img width="442" height="255" alt="Screenshot 2025-09-04 at 11 55 01 PM"
src="https://github.com/user-attachments/assets/703126f6-a448-49d9-9c02-daf3092cc7f9"
/>

---------

Co-authored-by: Muhsin <muhsinkeramam@gmail.com>

enterprise/app/models/channel/voice.rb

@@ -44,13 +44,13 @@ class Channel::Voice < ApplicationRecord
 
   # Public URLs used to configure Twilio webhooks
   def voice_call_webhook_url
-    base = ENV.fetch('FRONTEND_URL', '').to_s.sub(%r{/*$}, '')
-    "#{base}/twilio/voice/call/#{phone_number}"
+    digits = phone_number.delete_prefix('+')
+    "#{ENV.fetch('FRONTEND_URL', nil)}/twilio/voice/call/#{digits}"
   end
 
   def voice_status_webhook_url
-    base = ENV.fetch('FRONTEND_URL', '').to_s.sub(%r{/*$}, '')
-    "#{base}/twilio/voice/status/#{phone_number}"
+    digits = phone_number.delete_prefix('+')
+    "#{ENV.fetch('FRONTEND_URL', nil)}/twilio/voice/status/#{digits}"
   end
 
   private

enterprise/app/models/enterprise/conversation.rb

@@ -2,4 +2,15 @@ module Enterprise::Conversation
   def list_of_keys
     super + %w[sla_policy_id]
   end
+
+  # Include select additional_attributes keys (call related) for update events
+  def allowed_keys?
+    return true if super
+
+    attrs_change = previous_changes['additional_attributes']
+    return false unless attrs_change.is_a?(Array) && attrs_change[1].is_a?(Hash)
+
+    changed_attr_keys = attrs_change[1].keys
+    changed_attr_keys.intersect?(%w[call_status])
+  end
 end