New project under bootloader/ with the same structure as
color_switcher: Dockerfile, docker-compose, modular CMake, and
APP_BOOT + SYS_ECU stub components. Reuses common/ submodules for
MCU_UART, MCU_USB, HAL_COM, STD_TYPES.
TODO.md lists all open design decisions (interface, protocol, flash
layout, entry trigger, integrity checks, flash strategy) and the
implementation tasks that depend on them.
