Revert LLM back to nvidia/nemotron-3-nano-30b-a3b, update UI description

app.py

@@ -228,7 +228,7 @@ def show_home():
             </div>
             <div style="border-left: 1px solid #eee;">
                 <h4>🧬 Models</h4>
-                <p style="font-size: 0.85rem; color: #666;">NVIDIA Gemma 4 31B (Reasoning)<br>NVIDIA Nemotron Embed-1B (Vector)<br>NVIDIA Riva TTS (Audio)</p>
+                <p style="font-size: 0.85rem; color: #666;">NVIDIA Nemotron-3 (Reasoning)<br>NVIDIA Nemotron Embed-1B (Vector)<br>NVIDIA Riva TTS (Audio)</p>
             </div>
         </div>
     </div>

core/models.py

@@ -2,7 +2,7 @@ import os
 import streamlit as st
 from langchain_nvidia_ai_endpoints import ChatNVIDIA, NVIDIAEmbeddings
 
-def get_llm(model_name: str = "google/gemma-4-31b-it"):
+def get_llm(model_name: str = "nvidia/nemotron-3-nano-30b-a3b"):
     api_key = os.getenv("NV_API_KEY")
     if not api_key and "NV_API_KEY" in st.secrets:
         api_key = st.secrets["NV_API_KEY"]