feat(voice): Improved voice call creation flow [EE] (#12268)

This PR improves the voice call creation flow by simplifying
configuration and automating setup with Twilio APIs.

references: #11602 , #11481 

## Key changes

- Removed the requirement for twiml_app_sid – provisioning is now
automated through APIs.
- Auto-configured webhook URLs for:
  - Voice number callbacks
  - Status callbacks
  -  twiML callbacks
- Disabled business hours, help center, and related options until voice
inbox is fully supported.
- Added a configuration tab in the voice inbox to display the required
Twilio URLs (to make verification easier in Twilio console).


## Test Cases
- Provisioning
- Create a new voice inbox → verify that Twilio app provisioning happens
automatically.
  - Verify twiML callback 
- Webhook configuration
- Check that both voice number callback and status callback URLs are
auto-populated in Twilio.
- Disabled features
- Confirm that business hours and help center options are
hidden/disabled for voice inbox.
- Configuration tab
- Open the voice inbox configuration tab → verify that the displayed
Twilio URLs match what’s set in Twilio.

app/views/api/v1/models/_inbox.json.jbuilder

@@ -118,3 +118,9 @@ if resource.whatsapp?
   json.provider_config resource.channel.try(:provider_config) if Current.account_user&.administrator?
   json.reauthorization_required resource.channel.try(:reauthorization_required?)
 end
+
+## Voice Channel Attributes
+if resource.channel_type == 'Channel::Voice'
+  json.voice_call_webhook_url resource.channel.try(:voice_call_webhook_url)
+  json.voice_status_webhook_url resource.channel.try(:voice_status_webhook_url)
+end