fix: Setup webhooks for manual WhatsApp Cloud channel creation (#13278)

Fixes https://github.com/chatwoot/chatwoot/issues/13097

### Problem
The PR #12176 removed the `before_save :setup_webhooks` callback to fix
a race condition where Meta's webhook verification request arrived
before the channel was saved to the database. This change broke manual
WhatsApp Cloud channel setup. While embedded signup explicitly calls
`channel.setup_webhooks` in `EmbeddedSignupService`, manual setup had no
equivalent call - meaning the `subscribed_apps` endpoint was never
invoked and Meta never sent webhook events to Chatwoot.


### Solution
Added an `after_commit` callback that triggers webhook setup for manual
WhatsApp Cloud channels

app/models/channel/whatsapp.rb

@@ -34,6 +34,7 @@ class Channel::Whatsapp < ApplicationRecord
 
   after_create :sync_templates
   before_destroy :teardown_webhooks
+  after_commit :setup_webhooks, on: :create, if: :should_auto_setup_webhooks?
 
   def name
     'Whatsapp'
@@ -86,4 +87,10 @@ class Channel::Whatsapp < ApplicationRecord
   def teardown_webhooks
     Whatsapp::WebhookTeardownService.new(self).perform
   end
+
+  def should_auto_setup_webhooks?
+    # Only auto-setup webhooks for whatsapp_cloud provider with manual setup
+    # Embedded signup calls setup_webhooks explicitly in EmbeddedSignupService
+    provider == 'whatsapp_cloud' && provider_config['source'] != 'embedded_signup'
+  end
 end

app/services/whatsapp/embedded_signup_service.rb

@@ -16,6 +16,10 @@ class Whatsapp::EmbeddedSignupService
     validate_token_access(access_token)
 
     channel = create_or_reauthorize_channel(access_token, phone_info)
+    # NOTE: We call setup_webhooks explicitly here instead of relying on after_commit callback because:
+    # 1. Reauthorization flow updates an existing channel (not a create), so after_commit on: :create won't trigger
+    # 2. We need to run check_channel_health_and_prompt_reauth after webhook setup completes
+    # 3. The channel is marked with source: 'embedded_signup' to skip the after_commit callback
     channel.setup_webhooks
     check_channel_health_and_prompt_reauth(channel)
     channel