⚡️ E3V2 blank bg for S1 compatibility (#23822)

Marlin/src/lcd/e3v2/creality/dwin_lcd.cpp

@@ -49,6 +49,7 @@ void DWIN_Startup() {
   #if DISABLED(SHOW_BOOTSCREEN)
     DWIN_Frame_Clear(Color_Bg_Black); // MarlinUI handles the bootscreen so just clear here
   #endif
+  DWIN_JPG_ShowAndCache(3);
   DWIN_UpdateLCD();
 }
 

Marlin/src/lcd/e3v2/jyersui/dwin.cpp

@@ -4989,6 +4989,8 @@ void MarlinUI::init_lcd() {
     DWIN_UpdateLCD();
     delay(20);
   }
+
+  DWIN_JPG_ShowAndCache(3);
   DWIN_JPG_CacheTo1(Language_English);
   CrealityDWIN.Redraw_Screen();
 }

Marlin/src/lcd/e3v2/marlinui/dwin_lcd.cpp

@@ -45,6 +45,7 @@ void DWIN_Startup() {
   const bool success = DWIN_Handshake();
   if (success) DEBUG_ECHOLNPGM("ok."); else DEBUG_ECHOLNPGM("error.");
   DWIN_Frame_SetDir(TERN(DWIN_MARLINUI_LANDSCAPE, 0, 1));
+  DWIN_JPG_ShowAndCache(3);
   DWIN_Frame_Clear(Color_Bg_Black); // MarlinUI handles the bootscreen so just clear here
   DWIN_UpdateLCD();
 }

Marlin/src/lcd/e3v2/proui/dwin.cpp

@@ -1836,6 +1836,7 @@ void DWIN_Startup() {
   DWINUI::onCursorErase = Erase_Menu_Cursor;
   DWINUI::onTitleDraw = Draw_Title;
   DWINUI::onMenuDraw = Draw_Menu;
+  DWIN_JPG_ShowAndCache(3);
   HMI_SetLanguage();
 }
 
@@ -1937,6 +1938,7 @@ void DWIN_RebootScreen() {
   DWINUI::Draw_CenteredString(Color_White, 220, GET_TEXT_F(MSG_PLEASE_WAIT_REBOOT));
   DWIN_UpdateLCD();
   delay(500);
+  DWIN_JPG_ShowAndCache(3);
 }
 
 void DWIN_Redraw_screen() {