Extend the UART protocol to support writing and reading the heating
state, and reading individual pole NTC sensors and the heating pad NTC.
Cache NTC readings for query on demand. Move PID updates to a workqueue
to avoid blocking the timer IRQ context.
- Add CONFIG_SAMPLE_NTC to CMakeLists.txt and Kconfig
- Implement PI temperature controller with PWM output in heating.hpp
- Convert NtcGroup from template to non-template class
- Add LED helper class with flash support
- Implement COM protocol handlers for device ID and running state
- Add SPI, sensor, and PWM configuration to prj.conf
- Remove indicator overlay and update main.cpp with temperature
monitoring
- Add test script for serial protocol communication
