refactor: replace vi.doMock with vi.mock + vi.hoisted (#8319)

Replace `vi.doMock` with `vi.mock` + `vi.hoisted` pattern for cleaner
test mocking.

- Add ESLint rule to prevent future `doMock` usage
- Refactor `versionUtil.test.ts` and `firebaseAuthStore.test.ts`

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8319-refactor-replace-vi-doMock-with-vi-mock-vi-hoisted-2f46d73d365081ae9fccf2fa7471a75b)
by [Unito](https://www.unito.io)

Co-authored-by: Amp <amp@ampcode.com>

eslint.config.ts

@@ -240,6 +240,20 @@ export default defineConfig([
       ]
     }
   },
+  {
+    files: ['**/*.test.ts'],
+    rules: {
+      'no-restricted-properties': [
+        'error',
+        {
+          object: 'vi',
+          property: 'doMock',
+          message:
+            'Use vi.mock() with vi.hoisted() instead of vi.doMock(). See docs/testing/vitest-patterns.md'
+        }
+      ]
+    }
+  },
   {
     files: ['scripts/**/*.js'],
     languageOptions: {