split the wakeup now, properly working

semestralka_2/src/sleep/standby.rs

@@ -1 +1,13 @@
 // src/sleep/standby.rs
+
+pub fn enter_standby() -> ! {
+    unsafe extern "C" {
+        fn HAL_PWR_EnterSTANDBYMode();
+    }
+    
+    unsafe {
+        HAL_PWR_EnterSTANDBYMode();
+    }
+    
+    cortex_m::asm::udf(); // never happen marker
+}