What does this PR do?

Fixes the flaky no-show-updated-action.integration-test.ts that was failing intermittently across unrelated PRs (#27546, #26792, #27664) due to fragile inline Prisma operations and improper cleanup of dynamically created test data.

Root cause

This was the only booking-audit integration test that performed raw Prisma queries inside the test body. When integration tests run in parallel against a shared Postgres database, cascade deletes from other test files' cleanup (User → Booking → Attendee) could remove this test's data mid-execution, causing:

• PrismaClientKnownRequestError (P2025) — prisma.attendee.delete on an already-gone record
• BookingAuditPermissionError: BOOKING_NOT_FOUND — prisma.booking.findUnique returning null after cascade

Changes

1. Removed unnecessary prisma.booking.findUnique from beforeEach — it populated attendeeIds which was never read by any test
2. Stored booking.id in testData — eliminates the need to re-query the booking mid-test to get its ID
3. Replaced fragile prisma.attendee.delete (throws on missing) with proper afterEach cleanup via cleanupTestData (uses deleteMany, no-throw)
4. Added additionalAttendeeEmails tracking — second attendee created in "multiple attendees" test is now properly cleaned up via the shared afterEach, following the same pattern as accepted-action.integration-test.ts

How should this be tested?

Run all integration tests multiple times to verify the no-show test no longer flakes:

TZ=UTC VITEST_MODE=integration yarn test

Locally verified with 4 consecutive runs — the no-show test passed all 4 times. (Other pre-existing flaky tests like managedEventManualReassignment still fail intermittently, unrelated to this change.)

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A — test-only change.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Review checklist for humans

• Verify that attendeeIds was truly unused — it was populated but never referenced in any assertion
• Confirm booking.id is available from createTestBooking return value (it calls prisma.booking.create which returns all scalar fields)
• Note: import reordering and single-line array formatting are auto-applied by biome — no logic changes

Link to Devin run: https://app.devin.ai/sessions/1effb12fa2904b36a152dc3560f16eaf
Requested by: @hariombalhara