feat: create, publish, import and report on quizzes over MCP

- quizzes_create_quiz, update_quiz, delete_quiz (confirm repeats the
  slug), publish, unpublish, import_quiz (the existing import route) and
  quiz_stats on new manage routes
- stats close expired open test attempts first, then report per student
  over completed whole-quiz attempts and per question over every
  completed attempt
- input is checked before the database; TestManageAPIAgainstDatabase is
  written and skipped under -short

plugin_test.go

@@ -71,6 +71,12 @@ func TestRoutesRegistered(t *testing.T) {
 		"POST /api/v1/quizzes/import",
 		"GET /api/v1/quizzes",
 		"GET /api/v1/quizzes/{slug}",
+		"POST /api/v1/quizzes",
+		"PATCH /api/v1/quizzes/{slug}",
+		"DELETE /api/v1/quizzes/{slug}",
+		"POST /api/v1/quizzes/{slug}/publish",
+		"POST /api/v1/quizzes/{slug}/unpublish",
+		"GET /api/v1/quizzes/{slug}/stats",
 	}
 	var got []string
 	for _, r := range router.Routes() {