fix: fix wrong date calculation

backend/database.go

@@ -244,3 +244,43 @@ func DeleteUser(db *sql.DB, id int) error {
 	_, err := db.Exec("DELETE FROM users WHERE id = ?", id)
 	return err
 }
+
+func DeleteTimeEntriesByUserAndWeek(db *sql.DB, userID int, year int, week int) error {
+	query := `
+		DELETE FROM time_entries 
+		WHERE user_id = ? 
+		AND CAST(strftime('%W', date) AS INTEGER) = ? 
+		AND CAST(strftime('%Y', date) AS INTEGER) = ?
+	`
+	_, err := db.Exec(query, userID, week, year)
+	return err
+}
+
+func CheckUserHasEntriesForWeek(db *sql.DB, userID int, year int, week int) (bool, error) {
+	// Berechne die Daten der Woche
+	dates := calculateWeekDates(year, week)
+
+	// Hole alle Daten als Liste
+	var dateList []string
+	for _, date := range dates.Dates {
+		dateList = append(dateList, date)
+	}
+
+	// Prüfe ob Einträge existieren
+	query := `
+		SELECT COUNT(*) 
+		FROM time_entries 
+		WHERE user_id = ? 
+		AND date IN (?, ?, ?, ?, ?)
+	`
+
+	var count int
+	err := db.QueryRow(query, userID,
+		dateList[0], dateList[1], dateList[2], dateList[3], dateList[4]).Scan(&count)
+
+	if err != nil {
+		return false, err
+	}
+
+	return count > 0, nil
+}