CAMPER_DEMO=1 only works when Xcode or simctl launches the process, so
a build installed locally and opened from the home screen had no way
to enable demo mode at all. Demo mode is now also a persisted toggle
under Settings > Entwicklung (Debug builds only), checked alongside the
environment variable. Takes effect after an app restart since
DeviceStore/BluetoothManager only read it at init.
Also mark the demo leveling sensor as live-connected - it had a level
reading but never a live link state, which left the Ausrichtungs-
Assistent button (and Live Activity toggle) disabled in demo mode.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
