fix(core): fix display fatal error screen (T3T1)

[no changelog]

core/embed/rust/src/ui/model_mercury/mod.rs

@@ -21,6 +21,11 @@ impl UIFeaturesCommon for ModelMercuryFeatures {
         crate::ui::display::fade_backlight_duration(theme::BACKLIGHT_DIM, 150);
     }
 
+    fn backlight_on() {
+        #[cfg(feature = "backlight")]
+        crate::ui::display::set_backlight(theme::BACKLIGHT_NORMAL);
+    }
+
     const SCREEN: Rect = constant::SCREEN;
 
     fn screen_fatal_error(title: &str, msg: &str, footer: &str) {

core/embed/rust/src/ui/model_mercury/screens.rs

@@ -9,6 +9,7 @@ pub fn screen_fatal_error(title: &str, msg: &str, footer: &str) {
     let mut frame = ErrorScreen::new(title.into(), msg.into(), footer.into());
     frame.place(constant::screen());
     frame.paint();
+    display::refresh();
 }
 
 pub fn screen_boot_stage_2() {