feat(bookings): add overrideAvailability flag to v2 create endpoint

[GAURAV07C]

#29249
This PR is a continuation of #29254 which was previously closed due to inactivity.

It has been rebased on the latest main branch and includes fixes based on prior review feedback:

Fixed incorrect HTTP status handling:
401 Unauthorized for unauthenticated requests
403 Forbidden for authenticated users without required permissions
Fixed validation edge case where overrideAvailability: null could bypass boolean validation

[github-actions]

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR implements an organizer override feature allowing event type owners and org admins to create bookings that bypass availability checks and calendar conflict validation. The change adds an optional overrideAvailability boolean request field with authorization verification, propagates a skipAvailabilityCheck flag through all booking creation methods and into bookingMeta, updates OpenAPI schemas and endpoint documentation, and performs unrelated cleanup of deprecated webhook triggers.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding an overrideAvailability flag to the v2 create bookings endpoint, which matches the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The PR description is directly related to the changeset, explaining the addition of overrideAvailability flag and detailing specific HTTP status and validation fixes.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[CLAassistant]

All committers have signed the CLA.