feat: review open answers in the admin and pick a grader per quiz

- Do oceny admin screen (golem15.quizzes.reviews) over the open answers,
  with a read-only context partial, score and comment virtual fields saved
  through SetScore, confirm and regrade record actions, bulk confirm
- open question type, rubric and max_length in the question form; grader
  dropdown on the quiz form from the grader registry
- Review model with quiz, status and student filters

models/quizzes/fields.yaml

@@ -65,3 +65,10 @@ fields:
         type: number
         span: left
         comment: golem15.quizzes::lang.quizzes.max_attempts_comment
+    grader:
+        label: golem15.quizzes::lang.quizzes.grader
+        type: dropdown
+        span: right
+        default: manual
+        options: getGraderOptions
+        comment: golem15.quizzes::lang.quizzes.grader_comment