- event_recorder.c: add SET DRAWBOXENABLE 0/1 BLE command (runtime toggle,
INI-persistent); expose g_dwDrawBoxEnable extern
- kdp2_host_stream.c: guard draw-box and seg-overlay rendering behind
g_dwDrawBoxEnable so SET DRAWBOXENABLE 0 cleanly suppresses both
- handshake.c: derive key from runtime VMF_NNM_Get_Kn_Number() instead of
compile-time constant; each board gets a unique handshake key
- kp_firmware.c: remove startup handshake key print (key is now per-board,
fixed expected value is no longer meaningful)
- move base64.h / sha256.h / handshake.h from src/host_stream/ to
include/host_stream/ (proper include path for shared headers)
