fix(admin/models): make account->model and model->effort cascade fire on first pick

The account and model <select>s had no value="" placeholder option, so a
controlled value of "" made the browser display the first real entry as if
it were already chosen. Clicking that entry was not a change, so onChange
never fired and the cascade (account->catalog, model->efforts) only ran after
a *second*, different selection.

Prepend a real value="" placeholder option to both dropdowns so the displayed
value matches the controlled state and the first real selection now triggers
onChange as expected.

apps/web/src/app/(app)/admin/models/page.tsx

@@ -320,7 +320,7 @@ export default function AdminModelsPage() {
               options={
                 accountOptions.length === 0
                   ? [{ value: "", label: "اکانتی ثبت نشده — ابتدا اکانت agy بسازید" }]
-                  : accountOptions
+                  : [{ value: "", label: "اکانت agy را انتخاب کنید" }, ...accountOptions]
               }
               hint="کاتالوگ مدل‌ها از همین اکانت خوانده می‌شود."
             />
@@ -339,7 +339,7 @@ export default function AdminModelsPage() {
                     ? [{ value: "", label: "در حال بارگذاری کاتالوگ…" }]
                     : modelOptions.length === 0
                       ? [{ value: "", label: "کاتالوگی برای این اکانت نیست" }]
-                      : modelOptions
+                      : [{ value: "", label: "یک مدل انتخاب کنید" }, ...modelOptions]
               }
               disabled={!accountId || catalogLoading || modelOptions.length === 0}
             />