add linting and some lazy loading

frontend/eslint.config.mjs

@@ -0,0 +1,23 @@
+import tsParser from '@typescript-eslint/parser';
+
+export default [
+  {
+    ignores: ['dist/**', 'build/**', 'node_modules/**'],
+  },
+  {
+    files: ['src/**/*.{ts,tsx}', 'vite.config.ts', 'vitest.setup.ts'],
+    languageOptions: {
+      parser: tsParser,
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+      },
+    },
+    rules: {
+      'no-debugger': 'error',
+    },
+  },
+];