fix: Force Python 3.11 for Streamlit Cloud deployment

tiktoken==0.7.0 requires Rust compiler on Python 3.13 (no prebuilt wheels).
Using Python 3.11 to ensure smooth deployment on Streamlit Cloud.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: 2 people

.streamlit/config.toml

@@ -0,0 +1,6 @@
+[server]
+headless = true
+port = 8501
+
+[python]
+version = "3.11"