fix: refuse review writes while a test attempt is open

WR-02: Confirm and SetScore answer ErrAttemptOpen (409 attempt_open,
an admin refusal) for an answer of a running test, ConfirmBulk skips
such attempts, and the default open queue leaves them out, so
AnswerReviewed never fires before the test ends.

controllers/api/reviews.go

@@ -33,6 +33,8 @@ func writeReview(w http.ResponseWriter, status int, data any, err error) {
 		reviewConflict(w, "The answer is already reviewed; set the score instead.", "already_reviewed")
 	case errors.Is(err, classes.ErrGraderManual):
 		reviewConflict(w, "The quiz's grader is manual or not available, so nothing can be graded again.", "grader_manual")
+	case errors.Is(err, classes.ErrAttemptOpen):
+		reviewConflict(w, "The test attempt is still open; review its answers once it ends.", "attempt_open")
 	case errors.Is(err, classes.ErrNotFound):
 		wire.WriteJSON(w, http.StatusNotFound, map[string]any{"error": true, "message": "Open answer, attempt or quiz not found."})
 	default: