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.

config/locales/en.yml

@@ -185,6 +185,8 @@ en:
         removed: '%{user_name} removed %{labels}'
       sla:
         added: '%{user_name} added SLA policy %{sla_name}'
+      csat:
+        not_sent_due_to_messaging_window: 'CSAT survey not sent due to outgoing message restrictions'
         removed: '%{user_name} removed SLA policy %{sla_name}'
       muted: '%{user_name} has muted the conversation'
       unmuted: '%{user_name} has unmuted the conversation'