cleanup/small refactor + first tests

Backend/helper/time_test.go

@@ -0,0 +1,17 @@
+package helper
+
+import (
+	"testing"
+	"time"
+)
+
+func TestGetMonday(t *testing.T) {
+	isMonday, err := time.Parse("2006-01-02", "2025-07-14")
+	notMonday, err := time.Parse("2006-01-02", "2025-07-16")
+	if err != nil || isMonday == notMonday {
+		t.Errorf("U stupid? %e", err)
+	}
+	if GetMonday(isMonday) != isMonday || GetMonday(notMonday) != isMonday {
+		t.Error("Wrong date conversion!")
+	}
+}