feat(payments): auto-populate payment due date with middle session date upon class selection

src/views/payments/PaymentListView.vue

@@ -180,6 +180,7 @@ import { useToast } from '@/composables/useToast';
 import { paymentApi } from '@/api/paymentApi';
 import { userApi } from '@/api/userApi';
 import { classApi } from '@/api/classApi';
+import { sessionApi } from '@/api/sessionApi';
 import PageHeader from '@/components/common/PageHeader.vue';
 import DataTableWrapper from '@/components/common/DataTableWrapper.vue';
 import ConfirmDeleteDialog from '@/components/common/ConfirmDeleteDialog.vue';
@@ -263,7 +264,7 @@ const eligibleUsers = computed(() => {
   return usersList.value.filter((u) => eligibleIds?.has(String(u._id || u.id)));
 });
 
-const onClassesSelected = () => {
+const onClassesSelected = async () => {
   if (createForm.user && !eligibleUsers.value.some((u) => (u._id || u.id) === createForm.user)) {
     createForm.user = null;
   }
@@ -287,8 +288,24 @@ const onClassesSelected = () => {
   if ((createForm.discount || 0) > (createForm.amount || 0)) {
     createForm.discount = createForm.amount || 0;
   }
-  if (!createForm.dueDate) {
-    createForm.dueDate = getTodayJalali();
+
+  const selectedClassId = createForm.classes[createForm.classes.length - 1];
+  const selectedClass = classesList.value.find((item) => String(item._id || item.id) === String(selectedClassId));
+  if (selectedClass) {
+    try {
+      const res = await sessionApi.getAll({
+        class: selectedClassId,
+        sortBy: 'day',
+        sortOrder: 'asc',
+        limit: 100
+      });
+      const data = res.data || res;
+      const rawSessions = data.items || data.sessions || data.data || data || [];
+      const sessionList = Array.isArray(rawSessions) ? rawSessions : [];
+      createForm.dueDate = calculateClassMidDate(selectedClass, sessionList);
+    } catch (e) {
+      createForm.dueDate = calculateClassMidDate(selectedClass);
+    }
   }
 };