Fix anonymous access 500 error and add environment variable control

- Fixed dashboard.html template error accessing current_user.username for anonymous users
- Added ALLOW_ANONYMOUS_ACCESS environment variable with default true
- Enhanced index route logic to properly check config before allowing anonymous access
- Added proper environment variable to docker-compose.yml
- Anonymous access now works without 500 server errors

Fixes issue #2 completely - anonymous access is now functional

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

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

docker-compose.yml

@@ -40,6 +40,7 @@ services:
       FLASK_ENV: production
       DEBUG: "False"
       SECRET_KEY: ${SECRET_KEY:-change-this-secret-key-in-production}
+      ALLOW_ANONYMOUS_ACCESS: ${ALLOW_ANONYMOUS_ACCESS:-true}
 
       # Auth0 configuration (optional)
       AUTH0_DOMAIN: ${AUTH0_DOMAIN:-}