fix: Add missing CSAT URL in email reply templates (#11808)

As part of PR [#11622](https://github.com/chatwoot/chatwoot/pull/11622),
we intentionally hide CSAT survey URLs from agents in the dashboard to
avoid exposing those links internally. However, email replies being
external communications to contacts should still include the survey
URLs.

We missed handling that specific case for email channels. All other
external channels like WhatsApp, Instagram, Telegram, etc., were already
working correctly and continue to include the survey URLs as intended.

---------

Co-authored-by: Pranav <pranav@chatwoot.com>

spec/mailers/conversation_reply_mailer_spec.rb

@@ -154,6 +154,27 @@ RSpec.describe ConversationReplyMailer do
         expect(mail.message_id).to eq message.source_id
       end
 
+      context 'when message is a CSAT survey' do
+        let(:csat_message) do
+          create(:message, conversation: conversation, account: account, message_type: 'template',
+                           content_type: 'input_csat', content: 'How would you rate our support?', sender: agent)
+        end
+
+        it 'includes CSAT survey URL in outgoing_content' do
+          with_modified_env 'FRONTEND_URL' => 'https://app.chatwoot.com' do
+            mail = described_class.email_reply(csat_message).deliver_now
+            expect(mail.decoded).to include "https://app.chatwoot.com/survey/responses/#{conversation.uuid}"
+          end
+        end
+
+        it 'uses outgoing_content for CSAT message body' do
+          with_modified_env 'FRONTEND_URL' => 'https://app.chatwoot.com' do
+            mail = described_class.email_reply(csat_message).deliver_now
+            expect(mail.decoded).to include csat_message.outgoing_content
+          end
+        end
+      end
+
       context 'with email attachments' do
         it 'includes small attachments as email attachments' do
           message_with_attachment = create(:message, conversation: conversation, account: account, message_type: 'outgoing',