feat(sms): send class start date, days, and course time

Expose schedule fields on class and invoice templates so SMS can include Jalali start date, weekdays, and hour range.

utils/classSchedule.test.js

@@ -0,0 +1,59 @@
+'use strict';
+
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const {
+  formatCourseTime,
+  formatClassDays,
+  formatClassStartDate,
+  buildClassScheduleContext
+} = require('./classSchedule');
+
+describe('class schedule SMS helpers', () => {
+  it('formats course time as an hour range', () => {
+    assert.equal(formatCourseTime('19:00', '21:00'), 'از 19 تا 21');
+    assert.equal(formatCourseTime('19:30', '21:00'), 'از 19:30 تا 21');
+  });
+
+  it('joins class weekdays in Persian week order', () => {
+    const atNoon = (year, month, day) => new Date(year, month - 1, day, 12, 0, 0);
+    const monday = atNoon(2026, 8, 17);
+    const saturday = atNoon(2026, 8, 15);
+    const wednesday = atNoon(2026, 8, 19);
+
+    assert.equal(
+      formatClassDays([
+        { day: monday },
+        { day: saturday },
+        { day: wednesday },
+        { day: saturday }
+      ]),
+      'شنبه، دوشنبه و چهارشنبه'
+    );
+  });
+
+  it('builds start date, days, and course time from class and sessions', () => {
+    const atNoon = (year, month, day) => new Date(year, month - 1, day, 12, 0, 0);
+    const context = buildClassScheduleContext(
+      { startDate: atNoon(2026, 8, 15) },
+      [
+        { day: atNoon(2026, 8, 15), startTime: '19:00', endTime: '21:00' },
+        { day: atNoon(2026, 8, 17), startTime: '19:00', endTime: '21:00' }
+      ]
+    );
+
+    assert.ok(context.classStartDate);
+    assert.equal(context.classDays, 'شنبه و دوشنبه');
+    assert.equal(context.courseTime, 'از 19 تا 21');
+  });
+
+  it('uses the current session for course time when provided', () => {
+    const context = buildClassScheduleContext(
+      { startDate: new Date('2026-08-15T00:00:00Z') },
+      [{ day: new Date('2026-08-15T00:00:00Z'), startTime: '19:00', endTime: '21:00' }],
+      { startTime: '10:00', endTime: '12:00' }
+    );
+
+    assert.equal(context.courseTime, 'از 10 تا 12');
+  });
+});