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/shared_chat_service.py

@@ -264,7 +264,7 @@ class SharedChatService:
                 limit=memory_config.get("max_history", 10)
             )
             history = [
-                {"role": msg.role, "content": msg.content}
+                {"role": msg.role, "content": [{"type": "text", "text": msg.content}] + msg.meta_data.get("files", [])}
                 for msg in messages
             ]
 
@@ -472,7 +472,7 @@ class SharedChatService:
                     limit=memory_config.get("max_history", 10)
                 )
                 history = [
-                    {"role": msg.role, "content": msg.content}
+                    {"role": msg.role, "content": [{"type": "text", "text": msg.content}] + msg.meta_data.get("files", [])}
                     for msg in messages
                 ]