Convert all store files from JavaScript to TypeScript

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/components/ModalHeader.test.js

@@ -2,7 +2,7 @@ import { describe, it, expect, beforeEach, vi } from 'vitest';
 import { mount } from '@vue/test-utils';
 import { setActivePinia, createPinia } from 'pinia';
 import ModalHeader from '@/views/AccountManagement/ModalHeader.vue';
-import { useModalStore } from '@/stores/modal.js';
+import { useModalStore } from '@/stores/modal';
 
 describe('ModalHeader', () => {
   let pinia;