Release 2.0.0-alpha.50 #544

Prepare the release of 2.0.0-alpha.50, which brings the Cloud Registry component changes merged since v2.0.0-alpha.49 (needed by the Cloud Registry UI), the theming controls of #446 and the aligned release workflow (#517).

Following "Releases" in the contributing guide:

• run node scripts/release.js set 2.0.0-alpha.50 (versions of the root and of all released packages, package-lock.json, version and date-released in CITATION.cff)
• merge the version bump pull request (chore: release 2.0.0-alpha.50) into dev once CI has passed
• a maintainer tags the merge commit (v2.0.0-alpha.50), approves the npm environment and the staged versions, and fast-forwards main

Not part of this release: #509, #458 (cookie consent), #535, #516, #523.