debug: Add hello world test for HF Spaces restart cycle investigation

- Ultra-minimal hello_world.py with basic streamlit output
- Strip requirements.txt to just 'streamlit'
- Change app_file to hello_world.py in README.md
- Test if 5-minute restart cycle persists with minimal code
- Will isolate whether issue is infrastructure or code-related

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

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

README.md

@@ -4,7 +4,7 @@ emoji: 🎤📅
 colorFrom: blue
 colorTo: purple
 sdk: streamlit
-app_file: minimal_test.py
+app_file: hello_world.py
 pinned: false
 license: mit
 short_description: Voice-enabled AI assistant with WebRTC integration

hello_world.py

@@ -0,0 +1,4 @@
+import streamlit as st
+
+st.write("Hello World - VoiceCal HF Spaces Test")  
+st.write("If this stays running without restarting every 5 minutes, then the infrastructure is working.")

requirements.txt

@@ -1,14 +1,2 @@
-# Minimal requirements for Streamlit + WebSocket deployment
-streamlit>=1.28.0
-fastapi>=0.104.0
-uvicorn>=0.24.0
-
-# WebSocket support
-websockets>=12.0
-
-# Basic utilities only
-python-dotenv==1.0.0
-python-dateutil==2.8.2
-
-# For audio processing in WebRTC (minimal set)
-numpy>=1.21.0
+# Ultra-minimal for debugging restart loop
+streamlit