separaded endpoints + cleaned page templates + added constants to time formatting

Backend/endpoints/team.go

@@ -65,7 +65,7 @@ func showWeeks(w http.ResponseWriter, r *http.Request) {
 	submissionDate := r.URL.Query().Get("submission_date")
 	lastSub := user.GetLastWorkWeekSubmission()
 	if submissionDate != "" {
-		submissionDate, err := time.Parse("2006-01-02", submissionDate)
+		submissionDate, err := time.Parse(time.DateOnly, submissionDate)
 		if err == nil {
 			lastSub = helper.GetMonday(submissionDate)
 		}