STM32-006: Remove blocking do-while loop that waited for legacy GUI start
flag — production V7 PyQt GUI never sends it, hanging the MCU at boot.
STM32-004: Check ad9523_init() return code and call Error_Handler() on
failure, matching the pattern used by all other hardware init calls.
FPGA-001: Simplify frame boundary detection to only trigger on
chirp_counter wrap-to-zero. Previous conditions checking == N and == 2N
were unreachable dead code (counter wraps at N-1). Now correct for any
chirps_per_elev value.