fix(agetn features):

1. Historical multimodal message writing is incorporated into the conversation context;
2. Resolve the issues where csv, json, and txt files cannot be recognized due to encoding problems;
3. File quantity limit;
4. Error details

api/app/services/conversation_service.py

@@ -291,7 +291,7 @@ class ConversationService:
         history = [
             {
                 "role": msg.role,
-                "content": msg.content
+                "content": [{"type": "text", "text": msg.content}] + msg.meta_data.get("files", [])
             }
             for msg in messages
         ]