use cheaper model

app.py

@@ -67,7 +67,7 @@ class OpenAIHandler(StreamHandler):
         """Connect to realtime API. Run forever in separate thread to keep connection open."""
         self.client = openai.Client(api_key=api_key)
         with self.client.beta.realtime.connect(
-            model="gpt-4o-realtime-preview-2024-10-01"
+            model="gpt-4o-mini-realtime-preview-2024-12-17"
         ) as conn:
             conn.session.update(session={"turn_detection": {"type": "server_vad"}})
             self.connection = conn