Live key detection and improved Studio Analyzer layout

Restore live key detection and expand mobile analyzer view

Microphone and system audio now update a live key readout and Circle of Fifths indicator in the Studio Analyzer. The detector uses paired samples when available, falls back to Web Audio frequency data, suppresses weak estimates, and resets with the input. The key and beat header stays fixed in height, while mobile landscape uses compact controls and more space for the visualizations. Version 1.0.18.