Fix formation issue in simplified duration representation of AKSlot

Also use this representation in durations list of AK

AKModel/models.py

@@ -264,7 +264,7 @@ class AK(models.Model):
 
     @property
     def durations_list(self):
-        return ", ".join(str(slot.duration) for slot in self.akslot_set.all())
+        return ", ".join(str(slot.duration_simplified) for slot in self.akslot_set.all())
 
     @property
     def wish(self):
@@ -342,7 +342,7 @@ class AKSlot(models.Model):
         Display duration of slot in format hours:minutes, e.g. 1.5 -> "1:30"
         """
         hours, minutes = divmod(self.duration * 60, 60)
-        return f"{hours}:{minutes:2.0f}"
+        return f"{hours}:{minutes:02.0f}"
 
     @property
     def start_simplified(self):