refactor: rename firebaseAuthStore to authStore with shared test fixtures (#10483)

## Summary

Rename `useFirebaseAuthStore` → `useAuthStore` and
`FirebaseAuthStoreError` → `AuthStoreError`. Introduce shared mock
factory (`authStoreMock.ts`) to replace 16 independent bespoke mocks.

## Changes

- **What**: Mechanical rename of store, composable, class, and store ID
(`firebaseAuth` → `auth`). Created
`src/stores/__tests__/authStoreMock.ts` — a shared mock factory with
reactive controls, used by all consuming test files. Migrated all 16
test files from ad-hoc mocks to the shared factory.
- **Files**: 62 files changed (rename propagation + new test infra)

## Review Focus

- Mock factory API design in `authStoreMock.ts` — covers all store
properties with reactive `controls` for per-test customization
- Self-test in `authStoreMock.test.ts` validates computed reactivity

Fixes #8219

## Stack

This is PR 1/5 in a stacked refactoring series:
1. **→ This PR**: Rename + shared test fixtures
2. #10484: Extract auth-routing from workspaceApi
3. #10485: Auth token priority tests
4. #10486: Decompose MembersPanelContent
5. #10487: Consolidate SubscriptionTier type

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>

src/platform/workspace/api/workspaceApi.ts

@@ -2,7 +2,7 @@ import axios from 'axios'
 
 import { t } from '@/i18n'
 import { api } from '@/scripts/api'
-import { useFirebaseAuthStore } from '@/stores/firebaseAuthStore'
+import { useAuthStore } from '@/stores/authStore'
 
 export type WorkspaceType = 'personal' | 'team'
 export type WorkspaceRole = 'owner' | 'member'
@@ -288,7 +288,7 @@ const workspaceApiClient = axios.create({
 })
 
 async function getAuthHeaderOrThrow() {
-  const authHeader = await useFirebaseAuthStore().getAuthHeader()
+  const authHeader = await useAuthStore().getAuthHeader()
   if (!authHeader) {
     throw new WorkspaceApiError(
       t('toastMessages.userNotAuthenticated'),
@@ -300,7 +300,7 @@ async function getAuthHeaderOrThrow() {
 }
 
 async function getFirebaseHeaderOrThrow() {
-  const authHeader = await useFirebaseAuthStore().getFirebaseAuthHeader()
+  const authHeader = await useAuthStore().getFirebaseAuthHeader()
   if (!authHeader) {
     throw new WorkspaceApiError(
       t('toastMessages.userNotAuthenticated'),