feat(quizzes): module quiz history, archive endpoint, and quiz analytics

[davedumto]

Summary

• GET /courses/:id/modules/:moduleId/quiz-history: aggregate stats across every quiz in a module (average score, pass rate, total attempts, score distribution), admin-only, cached 5 minutes.
• POST /admin/courses/:id/modules/:moduleId/quizzes/:quizId/archive: a dedicated route delegating to the existing 0. Add POST /api/v1/admin/courses/:id/modules/:moduleId/quizzes/:quizId endpoint #413 update-quiz path with { archived: true/false }, same atomic transaction and audit log, added purely for discoverability over the generic update endpoint.
• GET /admin/courses/:id/modules/:moduleId/quizzes/:quizId/analytics: per-question correct rate and most common wrong answer, score distribution, and current-vs-superseded attempt counts. Per-question timing isn't tracked anywhere in the submission data (only questionId + selectedIndex), so it's explicitly reported as unavailable rather than fabricated.

Both aggregate endpoints are cached 5 minutes via the existing cacheGetOrSet helper and invalidated on every quiz write path.

Issue #468 (duplicate imports in course.service.ts) was already fixed on main before this branch was created; verified and made no changes for it.

closes #415
closes #416
closes #417
closes #468

Test plan

• New test file (tests/unit/quizzes/admin-quiz-analytics.test.ts, 16 cases): aggregate shape correctness, zero-submission edge cases, 5-minute cache-hit behavior, score bucketing, common-wrong-answer aggregation, superseded-vs-current counting, archive/unarchive delegation + audit log, 404s for mismatched course/module/quiz
• Full suite: 254 passed / 10 failed, all 10 failures pre-existing on main and unrelated to any file this PR touches (confirmed by diffing failure lists before/after)
• npx tsc --noEmit: clean on every file this PR touches
• eslint: 0 errors on changed files