Revert: Move VueFire persistence configuration to initialization (#5614) (#5729)

## Summary
This reverts PR #5614 which moved VueFire persistence configuration to
initialization.

## Reason for Revert

It breaks Google SSO login with error:

```
useErrorHandling.ts:12 FirebaseError: Firebase: Error (auth/argument-error).
    at createErrorInternal (index-c92d61ad.js:506:41)
    at _assert (index-c92d61ad.js:512:15)
    at _withDefaultResolver (index-c92d61ad.js:9237:5)
    at signInWithPopup (index-c92d61ad.js:9457:30)
    at executeAuthAction.createCustomer (firebaseAuthStore.ts:263:25)
    at executeAuthAction (firebaseAuthStore.ts:223:28)
    at Proxy.loginWithGoogle (firebaseAuthStore.ts:262:5)
    at Proxy.wrappedAction (pinia.mjs:1405:26)
    at useFirebaseAuthActions.ts:104:28
    at Object.signInWithGoogle (useErrorHandling.ts:39:22)
```

## Changes
- Reverts commit ea4e57b60 "Move VueFire persistence configuration to
initialization (#5614)"
- Restores previous Firebase auth persistence behavior

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5729-Revert-Move-VueFire-persistence-configuration-to-initialization-5614-2776d73d3650814c9b80d9c67c852874)
by [Unito](https://www.unito.io)

tests-ui/tests/store/firebaseAuthStore.test.ts

@@ -150,6 +150,13 @@ describe('useFirebaseAuthStore', () => {
     expect(store.loading).toBe(false)
   })
 
+  it('should set persistence to local storage on initialization', () => {
+    expect(firebaseAuth.setPersistence).toHaveBeenCalledWith(
+      mockAuth,
+      firebaseAuth.browserLocalPersistence
+    )
+  })
+
   it('should properly clean up error state between operations', async () => {
     // First, cause an error
     const mockError = new Error('Invalid password')