🚸 Wait for cooldown in MarlinUI power-off (#23476)

Marlin/src/lcd/marlinui.cpp

@@ -1553,11 +1553,13 @@ constexpr uint8_t epps = ENCODER_PULSES_PER_STEP;
     TERN_(HAS_LCD_MENU, return_to_status());
   }
 
-  #if BOTH(PSU_CONTROL, PS_OFF_CONFIRM)
+  #if BOTH(HAS_LCD_MENU, PSU_CONTROL)
+
     void MarlinUI::poweroff() {
-      queue.inject(F("M81"));
-      goto_previous_screen();
+      queue.inject(F("M81" TERN_(POWER_OFF_WAIT_FOR_COOLDOWN, "S")));
+      return_to_status();
     }
+
   #endif
 
   void MarlinUI::flow_fault() {

Marlin/src/lcd/marlinui.h

@@ -373,7 +373,7 @@ public:
     static void resume_print();
     static void flow_fault();
 
-    #if BOTH(PSU_CONTROL, PS_OFF_CONFIRM)
+    #if BOTH(HAS_LCD_MENU, PSU_CONTROL)
       static void poweroff();
     #endif
 

Marlin/src/lcd/menu/menu_main.cpp

@@ -380,7 +380,7 @@ void menu_main() {
           GET_TEXT(MSG_SWITCH_PS_OFF), (const char *)nullptr, PSTR("?")
         );
       #else
-        GCODES_ITEM(MSG_SWITCH_PS_OFF, PSTR("M81"));
+        ACTION_ITEM(MSG_SWITCH_PS_OFF, ui.poweroff);
       #endif
     else
       GCODES_ITEM(MSG_SWITCH_PS_ON, PSTR("M80"));