Add group-class enrolment deadline with instructor late-enrolment override

Group classes gain an instructor-set enrolment deadline (new
us_offerings.enrollment_deadline column) that defaults to the first day of
the class (term_start). Past the deadline students can no longer self-enrol:
the enrolment endpoint rejects it (403 enrollment_closed) and the front-end
class list shows "Enrolment has closed." in place of the Enrol button.

Instructors keep a manual path: the "Add students directly" control on each
class's details page now renders for public classes too (not just
invite-only) and deliberately bypasses the deadline and capacity, so a
student can be added as a late enrolment after the class has closed. Past
the deadline the details page labels these as late enrolments.

Bumps USC_VERSION to 1.1.3 for the schema change.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

assets/js/group-classes.js

@@ -103,6 +103,21 @@
         return [termLabel(o), timeLabel(o)].filter(Boolean).join(' · ');
     }
 
+    // Today as a Y-m-d string in the visitor's local timezone, for lexicographic
+    // comparison against the class's Y-m-d enrolment deadline.
+    function todayYmd() {
+        const now = new Date();
+        return `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}-${String(now.getDate()).padStart(2, '0')}`;
+    }
+
+    // Enrolment closes at the end of the deadline day — the instructor's set
+    // deadline, or the first class day by default. Mirrors the server-side
+    // Offering::isEnrollmentOpen() gate.
+    function isEnrollmentOpen(o) {
+        const deadline = o.enrollment_deadline || o.term_start || '';
+        return !deadline || todayYmd() <= deadline;
+    }
+
     function renderClasses(offerings, enrolledOfferingIds) {
         let groups = offerings.filter((o) => o.kind === 'group_class');
         if (singleOfferingId) {
@@ -125,7 +140,9 @@
                 <p>${escHtml(Number(o.price).toFixed(2))} ${escHtml(o.currency)}</p>
                 ${enrolledOfferingIds.has(Number(o.id))
         ? '<p class="us-enrolled"><strong>You are enrolled in this class.</strong></p>'
-        : `<button data-offering-id="${o.id}" class="us-enrol-btn">Enrol</button>`}
+        : (isEnrollmentOpen(o)
+            ? `<button data-offering-id="${o.id}" class="us-enrol-btn">Enrol</button>`
+            : '<p class="us-enrol-closed"><strong>Enrolment has closed.</strong></p>')}
             </div>
         `).join('');