feat: legacy features to ruby llm (#12994)

app/models/message.rb

@@ -254,6 +254,21 @@ class Message < ApplicationRecord
     Messages::SearchDataPresenter.new(self).search_data
   end
 
+  # Returns message content suitable for LLM consumption
+  # Falls back to audio transcription or attachment placeholder when content is nil
+  def content_for_llm
+    return content if content.present?
+
+    audio_transcription = attachments
+                          .where(file_type: :audio)
+                          .filter_map { |att| att.meta&.dig('transcribed_text') }
+                          .join(' ')
+                          .presence
+    return "[Voice Message] #{audio_transcription}" if audio_transcription.present?
+
+    '[Attachment]' if attachments.any?
+  end
+
   private
 
   def prevent_message_flooding