fix: weekbased calculation pdf report

with this change the time calculations for pdf reports should be better
line with the reports send as "week_report"

Backend/helper/time_test.go

@@ -26,6 +26,101 @@ func TestGetMonday(t *testing.T) {
 	}
 }
 
+func TestIsMonday_ReturnsTrueForMonday(t *testing.T) {
+	monday := time.Date(2023, 4, 3, 0, 0, 0, 0, time.UTC)
+
+	if !IsMonday(monday) {
+		t.Errorf("Expected IsMonday to return true for Monday, got false")
+	}
+}
+
+func TestIsMonday_ReturnsFalseForNonMonday(t *testing.T) {
+	tuesday := time.Date(2023, 4, 4, 0, 0, 0, 0, time.UTC)
+
+	if IsMonday(tuesday) {
+		t.Errorf("Expected IsMonday to return false for Tuesday, got true")
+	}
+}
+
+func TestGenerateDateRange(t *testing.T) {
+	start := time.Date(2026, 2, 9, 0, 0, 0, 0, time.UTC)
+	end := time.Date(2026, 2, 11, 0, 0, 0, 0, time.UTC)
+
+	dates := GenerateDateRange(start, end)
+
+	if len(dates) != 3 {
+		t.Fatalf("expected 3 dates, got %d", len(dates))
+	}
+
+	expected := []string{"2026-02-09", "2026-02-10", "2026-02-11"}
+	for i, d := range dates {
+		got := d.Format("2006-01-02")
+		if got != expected[i] {
+			t.Errorf("expected %s, got %s", expected[i], got)
+		}
+	}
+}
+
+func TestGetMondays_ReturnsOnlyMondays(t *testing.T) {
+	startDate := time.Date(2026, 01, 01, 0, 0, 0, 0, time.UTC)
+	endDate := time.Date(2026, 01, 31, 0, 0, 0, 0, time.UTC)
+
+	daysInMonth := GenerateDateRange(startDate, endDate)
+	result := GetMondays(daysInMonth, false)
+	if len(result) < 5 {
+		t.Errorf("Expected 5 monday, got %d", len(result))
+	} else if len(result) > 5 {
+		t.Errorf("Expected 5 monday, got %d", len(result))
+	}
+
+	if result[0] != time.Date(2025, 12, 29, 0, 0, 0, 0, time.UTC) {
+		t.Errorf("Expected first monday to be %v, got %v", "2025-12-29", result[0])
+	}
+}
+
+func TestGetMondays_ReturnsOnlyMondaysInRange(t *testing.T) {
+	startDate := time.Date(2026, 01, 01, 0, 0, 0, 0, time.UTC)
+	endDate := time.Date(2026, 01, 31, 0, 0, 0, 0, time.UTC)
+
+	daysInMonth := GenerateDateRange(startDate, endDate)
+	result := GetMondays(daysInMonth, true)
+	if len(result) < 4 {
+		t.Errorf("Expected 4 monday, got %d", len(result))
+	} else if len(result) > 4 {
+		t.Errorf("Expected 4 monday, got %d", len(result))
+	}
+
+	if result[0] != time.Date(2026, 1, 5, 0, 0, 0, 0, time.UTC) {
+		t.Errorf("Expected first monday to be %v, got %v", "2026-01-05", result[0])
+	}
+}
+
+func TestDaysInRange(t *testing.T) {
+	days := []time.Time{
+		time.Date(2023, 4, 3, 0, 0, 0, 0, time.UTC), // Tuesday
+		time.Date(2023, 4, 4, 0, 0, 0, 0, time.UTC), // Wednesday
+		time.Date(2023, 4, 5, 0, 0, 0, 0, time.UTC), // Thursday
+		time.Date(2023, 4, 6, 0, 0, 0, 0, time.UTC), // Friday
+	}
+
+	start := time.Date(2023, 4, 3, 0, 0, 0, 0, time.UTC)
+	end := time.Date(2023, 4, 5, 0, 0, 0, 0, time.UTC)
+
+	daysInRange := DaysInRange(days, start, end)
+
+	if len(daysInRange) != 3 {
+		t.Errorf("Expected 3 days in range, got %d", len(daysInRange))
+	}
+
+	if daysInRange[0] != days[0] {
+		t.Errorf("Expected first day in range to be %v, got %v", days[0], daysInRange[0])
+	}
+
+	if daysInRange[2] != days[2] {
+		t.Errorf("Expected third day in range to be %v, got %v", days[2], daysInRange[2])
+	}
+}
+
 func TestFormatDurationFill(t *testing.T) {
 	testCases := []struct {
 		name     string