fixed overtime calc issue

Backend/models/compoundDay.go

@@ -28,7 +28,7 @@ func (c *CompoundDay) GetWorkDay() WorkDay {
 
 // IsEmpty implements [IWorkDay].
 func (c *CompoundDay) IsEmpty() bool {
-	return len(c.DayParts) > 0
+	return len(c.DayParts) == 0
 }
 
 // Date implements [IWorkDay].
@@ -47,12 +47,16 @@ func (c *CompoundDay) GetDayProgress(u User) int8 {
 
 // GetOvertime implements [IWorkDay].
 func (c *CompoundDay) GetOvertime(u User, base WorktimeBase, includeKurzarbeit bool) time.Duration {
+	work := c.GetWorktime(u, base, includeKurzarbeit)
+	var targetHours time.Duration
 
-	var overtime time.Duration
-	for _, day := range c.DayParts {
-		overtime += day.GetOvertime(u, base, includeKurzarbeit)
+	switch base {
+	case WorktimeBaseDay:
+		targetHours = u.ArbeitszeitProTagFrac(1)
+	case WorktimeBaseWeek:
+		targetHours = u.ArbeitszeitProWocheFrac(.2)
 	}
-	return overtime
+	return (work - targetHours).Round(time.Minute)
 }
 
 // GetPausetime implements [IWorkDay].