test(web): extract shared test helpers for the three page tests

Adds apps/web/__tests__/helpers/test-utils.ts exporting reusable
factories and a small UI helper:

- mockCreatorProfile / defaultCreatorProfile
- mockPlaylist / defaultPlaylist / mockMyPlaylistsList (envelope) /
  mockPlaylistEnvelope (envelope)
- defaultFanProfile / defaultMeUser / mockMeResponse
- defaultAuth (preserves explicit null via in-checks)
- openCreateForm (UI helper)

Rewrites consume from helpers:
- creator-profile-page.test.tsx (12 tests, unchanged from previous commit)
- playlists-page.test.tsx (12 tests)
- edit-profile-page.test.tsx (10 tests)

Bug fixes that fell out of the rewrite:
- playlists-page mock module was exporting getMyPlaylists, but the
  page imports listMyPlaylists — rename to listMyPlaylists resolves
  "Failed to load playlists" on every data-load test.
- mockCreatePlaylist now returns mockPlaylistEnvelope(...) to match
  the { data: PlaylistResponse } shape createPlaylist produces.
- Edit-profile Loading test typed Promise<void> resolving undefined,
  which made the page access state.data.user on undefined. Now
  Promise<MeResponse> resolved with mockMeResponse().
- Edit-profile validation test changed to use a 1-char displayName
  ("X") that actually fails updateMeSchema.min(2) and asserts the
  error AFTER clicking submit (form only validates on submit).
- Edit-profile empty-fields test disambiguates the Genre label with
  an exact match so it no longer matches "Genre Preferences".
- Playlists load-error test drops name option from findByRole since
  <p role="alert"> computed accessible names are inconsistent.
- Removes an unused eslint-disable directive on DEFAULT_GENRE_PREFS.

Result: 50/50 tests pass across 6 files. Lint clean. Build clean.

Author: sheyman546

apps/web/__tests__/creator-profile-page.test.tsx

@@ -2,33 +2,7 @@ import { render, screen } from '@testing-library/react'
 import type { CreatorProfileResponse } from '@universal-healthcare/shared'
 import { describe, expect, it, vi } from 'vitest'
 import CreatorProfilePage from '../app/creators/[slug]/page'
-
-// ─────────────────────────────────────────────────────────────────────────────
-//  Mock fixtures
-// ─────────────────────────────────────────────────────────────────────────────
-
-const defaultCreatorProfile: CreatorProfileResponse = {
-  id: 'cp-1',
-  userId: 'u-1',
-  displayName: 'Solar Vibes',
-  slug: 'solar-vibes',
-  bio: 'Indie producer from Lagos',
-  avatarUrl: null,
-  genre: 'Indie',
-  location: 'Lagos',
-  isVerified: true,
-  followerCount: 0,
-  trackCount: 0,
-  createdAt: '2026-01-01T00:00:00.000Z',
-  updatedAt: '2026-01-01T00:00:00.000Z',
-}
-
-// Spread defaults first, then overrides — this preserves callers' explicit
-// `null` overrides (a `??`-based defaulting helper would silently coerce
-// `null` back to the default).
-const mockCreatorProfile = (
-  overrides?: Partial<CreatorProfileResponse>
-): CreatorProfileResponse => ({ ...defaultCreatorProfile, ...overrides })
+import { mockCreatorProfile } from './helpers/test-utils'
 
 // Hoisted so vi.mock factories can reference them.
 const { mockGetCreatorBySlug, mockUseParams } = vi.hoisted(() => ({