[Copilot]

Students had no way to view exams they had already submitted. Instructors could see aggregate scores but couldn't drill into a student's individual answers.

New API endpoint

GET /exam/submission?attempt_id={id}&user_id={id} — returns full submission detail: each question, all answer choices, the student's selection, and per-question correctness. Authorization: students can only access their own attempts; admins can access any.

// ExamStudentResult and ExamInfo now carry AttemptID so the frontend
// can link directly to the review page without a secondary lookup.
type ExamStudentResult struct {
    ...
    AttemptID *int `json:"attempt_id,omitempty"`
}

Both GetExamStatus and GetAssignedExamsForUser SQL queries updated to select att.id; InMemoryDB implementations updated to match.

New pages

• /exam-center.html — dedicated student Exam Center (replaces the inline dashboard panel). Two sections: pending exams (Start button) and submitted exams (View Submission + Retake).
• /exam-review.html — per-attempt review showing each question with the student's answer highlighted (✅ correct / ❌ wrong / ✓ correct-not-selected). Works for both students and instructors (admins see any attempt).

Changes to existing pages

• Dashboard — "Assigned Exams" inline button replaced by an "Exam Center" link with a pending-count badge.
• admin-exams.html scoring table — "View Submission" link added to each completed row (uses the instructor's own user_id as the requesting user, satisfying the admin auth check on the new endpoint).

• Fixes Students need to see submitted exams #172