Add CACHE_STATUS UART poll and dashboard live stream.

Combine cached accel and tap in one low-overhead master command for ~16 ms
host polling. The dashboard uses a single live-stream toggle plus per-slave
accel-stream controls; fix live_stream state so polling is not cleared every
slow client refresh.

Co-authored-by: Cursor <cursoragent@cursor.com>

main/powerpod.c

@@ -5,6 +5,7 @@
 #include "cmd_accel_stream.h"
 #include "cmd_tap_notify.h"
 #include "cmd_tap_snapshot.h"
+#include "cmd_cache_status.h"
 #include "cmd_espnow_unicast_test.h"
 #include "cmd_espnow_find_me.h"
 #include "cmd_restart.h"
@@ -186,6 +187,7 @@ void app_main(void) {
     cmd_accel_stream_register();
     cmd_tap_notify_register();
     cmd_tap_snapshot_register();
+    cmd_cache_status_register();
     cmd_espnow_unicast_test_register();
     cmd_espnow_find_me_register();
     cmd_restart_register();