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/javascript/shared/mixins/inboxMixin.js

@@ -57,15 +57,15 @@ export default {
     isALineChannel() {
       return this.channelType === INBOX_TYPES.LINE;
     },
+    isAVoiceChannel() {
+      return this.channelType === INBOX_TYPES.VOICE;
+    },
     isAnEmailChannel() {
       return this.channelType === INBOX_TYPES.EMAIL;
     },
     isATelegramChannel() {
       return this.channelType === INBOX_TYPES.TELEGRAM;
     },
-    isAVoiceChannel() {
-      return this.channelType === INBOX_TYPES.VOICE;
-    },
     isATwilioSMSChannel() {
       const { medium: medium = '' } = this.inbox;
       return this.isATwilioChannel && medium === 'sms';