Improve and Cleanup Shutdown callbacks (#21060)

Co-authored-by: Dasky <32983009+daskygit@users.noreply.github.com>

keyboards/bemeier/bmek/bmek.c

@@ -15,9 +15,12 @@
  */
 #include "quantum.h"
 
-__attribute__((weak))
-void shutdown_user(void) {
+bool shutdown_kb(bool jump_to_bootloader) {
+    if (!shutdown_user(jump_to_bootloader)) {
+        return false;
+    }
 #ifdef RGBLIGHT_ENABLE
     rgblight_setrgb(255, 0, 0);
 #endif
+    return true;
 }