Fix config file extension mismatch in start.sh - use TOML not JSON

The start.sh script was trying to load config-stt-en_fr-hf.json but only
config-stt-en_fr-hf.toml exists, causing moshi-server startup failure.

- Fix: Change start.sh to use .toml extension to match existing file
- Version bump: 4.0.5 → 4.0.6

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

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

VERSION

@@ -1 +1 @@
-4.0.5
+4.0.6

start.sh

@@ -21,7 +21,7 @@ echo "Starting Python frontend and official moshi-server..."
 
 # Start moshi-server in background
 cd /app
-moshi-server worker --config configs/config-stt-en_fr-hf.json &
+moshi-server worker --config configs/config-stt-en_fr-hf.toml &
 MOSHI_PID=$!
 
 # Wait a moment for moshi-server to start