Refine must-have features display in AI chat responses

- Updated the system message construction in the `chat_with_session_memory` function to improve the handling of must-have property features.
- Introduced a separate variable for must-have features to enhance readability and ensure that the display logic is clear and concise.
- This change ensures that if no must-have features are provided, the response defaults to '[none]', improving user experience and clarity in property inquiries.

ai_chat.py

@@ -29,11 +29,12 @@ def chat_with_session_memory(state):
     )
     
     intent_data = state.get("intent", {})
+    must_have_list = intent_data.get('must_have', []) or []
     system_message += (
         f" They're looking for a property in {intent_data.get('location_preference','[any area]')}, "
         f"with a budget up to {intent_data.get('budget','[any amount]')} per month, "
         f"around {intent_data.get('size_preference_sqm','[size]')} sqm, "
-        f"and must-haves: {', '.join(intent_data.get('must_have',[])) or '[none]'}. "
+        f"and must-haves: {', '.join(must_have_list) if must_have_list else '[none]'}. "
     )
     
     # Build messages array with history