The mic_gain_db template number had a set_action but no optimistic flag, so
TemplateNumber::control() never published the new value: the ES7210 was
reprogrammed but HA kept showing the old value and the slider snapped back.
TemplateNumber::setup() also only publishes the restored value without running
set_action, so a gain saved in flash showed in HA while the codec booted with
the default from audio_adc. Apply it to the ES7210 in on_boot (-100), which is
safe because set_mic_gain() stores the value even before setup completes.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
