[15.5.x] Fix CI (#94281)
Backports:
1. #86157
The other fixes are due to tests using unpinned versions. The latest
versions (e.g. Tailwind or `eslint-config-next`) are no longer
compatible with Node.js 18 (used in Next.js 15 CI).
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Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
