Convert all store files from JavaScript to TypeScript

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

tests/stores/modal.test.js

@@ -1,6 +1,6 @@
 import { describe, it, expect, beforeEach } from 'vitest';
 import { setActivePinia, createPinia } from 'pinia';
-import { useModalStore } from '@/stores/modal.js';
+import { useModalStore } from '@/stores/modal';
 import { MODAL_ACCT_INFO, MODAL_DELETE } from '@/constants/constants.js';
 
 describe('modalStore', () => {