feat: complete exam lifecycle — AI generation, submission, student session, and results

- Backend: AI generation fallbacks when OpenAI not configured, full exam
  submission saving all params (difficulty, rubric, entity, grading system,
  approval workflow) and creating linked question records per section
- Backend: new exam session controller with get_session, autosave, submit,
  status, and results endpoints; student attempt/answer/score models
- Backend: new controllers for entities, approval workflows, exam schedules
- Frontend: exam session split-layout with passage panel, question types
  (MCQ, T/F/NG, gap-fill, writing, speaking), timer, and review dialog
- Frontend: results page with percentage score, per-answer breakdown table
- Frontend: generation page dynamic dropdowns, full payload submission
- Frontend: updated types for ExamSessionSection, ExamQuestion options

Made-with: Cursor

custom_addons/encoach_exam_template/models/rubric.py

@@ -11,6 +11,7 @@ class EncoachRubric(models.Model):
         ('speaking', 'Speaking'),
     ], required=True)
     criteria = fields.Text(required=True)
+    levels = fields.Text(help='JSON list of CEFR levels, e.g. ["A1","A2","B1","B2","C1","C2"]')
     exam_type = fields.Selection([
         ('academic', 'Academic'),
         ('general_training', 'General Training'),