feat: add delete schoolyear route and handler

backend/database.go

@@ -580,3 +580,31 @@ func calculateHours(entry TimeEntry) float64 {
 		return calculateHoursDiff(entry.StartTime, entry.EndTime)
 	}
 }
+
+func DeleteSchoolYear(db *sql.DB, id int) error {
+	var isActive bool
+	err := db.QueryRow("SELECT is_active FROM school_years WHERE id = ?", id).Scan(&isActive)
+	if err != nil {
+		return err
+	}
+
+	if isActive {
+		return fmt.Errorf("cannot delete active school year")
+	}
+
+	result, err := db.Exec("DELETE FROM school_years WHERE id = ? AND is_active = 0", id)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return sql.ErrNoRows
+	}
+
+	return nil
+}

backend/handlers.go

@@ -690,3 +690,26 @@ func (app *App) GenerateYearlySummaryPDFHandler(c echo.Context) error {
 
 	return c.Blob(http.StatusOK, "application/pdf", pdfBytes)
 }
+
+func (app *App) DeleteSchoolYearHandler(c echo.Context) error {
+	id, err := strconv.Atoi(c.Param("id"))
+	if err != nil {
+		return HandleError(c, ErrInvalidInputMsg("Schuljahr-ID"))
+	}
+
+	if err := DeleteSchoolYear(app.DB, id); err != nil {
+		if err == sql.ErrNoRows {
+			return HandleError(c, ErrNotFoundMsg("Schuljahr"))
+		}
+		if err.Error() == "cannot delete active school year" {
+			return HandleError(c, &AppError{
+				Code:       "CANNOT_DELETE_ACTIVE_SCHOOL_YEAR",
+				Message:    "Aktives Schuljahr kann nicht gelöscht werden",
+				HTTPStatus: http.StatusBadRequest,
+			})
+		}
+		return HandleError(c, ErrDatabaseMsg(err))
+	}
+
+	return c.NoContent(http.StatusNoContent)
+}

backend/main.go

@@ -80,6 +80,7 @@ func main() {
 		admin.POST("/time-entry", app.AdminCreateTimeEntryHandler)
 		admin.GET("/school-years", app.GetSchoolYearsHandler)
 		admin.POST("/school-years", app.CreateSchoolYearHandler)
+		admin.DELETE("/school-years/:id", app.DeleteSchoolYearHandler)
 		admin.PUT("/school-years/:id/activate", app.SetActiveSchoolYearHandler)
 		admin.GET("/yearly-summary/pdf", app.GenerateYearlySummaryPDFHandler)
 	}