fix: Send CSAT survey only when agent can reply in conversation (#11584)

Fixes https://github.com/chatwoot/chatwoot/issues/11569

 ## Problem
On platforms like WhatsApp and Facebook Messenger, customers cannot
reply to messages after 24 hours (or other channel-specific messaging
windows). Despite this limitation, the system continued sending CSAT
surveys to customers outside their messaging window, making it
impossible for them to respond.

  ## Solution
Added a check for `conversation.can_reply?` in the
`should_send_csat_survey?` method. This leverages the existing
`MessageWindowService` which already handles all channel-specific
messaging window logic.

app/models/concerns/csat_activity_message_handler.rb

@@ -0,0 +1,8 @@
+module CsatActivityMessageHandler
+  extend ActiveSupport::Concern
+
+  def create_csat_not_sent_activity_message
+    content = I18n.t('conversations.activity.csat.not_sent_due_to_messaging_window')
+    ::Conversations::ActivityMessageJob.perform_later(self, activity_message_params(content)) if content
+  end
+end