- NodePrefs: add buzzer_volume field (0=min..4=max, default 4)
- DataStore: persist buzzer_volume at end of prefs file (backward-compat)
- buzzer: setVolume()/getVolume(); applyVolume() sets PWM duty cycle via
analogWrite() after each rtttl::play() call to control output amplitude
- Settings UI: new BzrVol bar item in Sound section (left/right to adjust)
- UITask: apply saved volume on startup alongside brightness
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
buzzer.play() was returning early when _is_quiet=true, so channels with
explicit notification=ON were silent even though the logic correctly set
play=true. playForced() bypasses the quiet check for these overrides.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>