chore(deps): upgrade MUI to v9.0.1

refactor(audio): split bidirectional viz into per-channel spectrums

feat(ui): bidirectional spectrum viz, minimal aesthetic pass

refactor(ui): proper channel columns, opaque joystick, design polish

feat(ui,audio): opaque joystick, auto-unmute on stream, VU meters

fix(lifecycle,ui): straddle joystick on video edge, side-by-side volumes, fix wake-up detection

feat(ui): joystick overlay on video, compact audio card

feat: initial Reachy Mini telepresence app