v21.0.0 ulmo release

[ahmed-arb]

v20.0.0 teak release

Epic: Ulmo Sandbox and Release Preparation

Todos before merge

• [x] Ensure changelog-entry exists for ulmo upgrade
• [ ] Ensure changelog exists for v21
• [ ] Ensure CI/Tests are working as expected
• [ ] Ensure ulmo branch is up-to-date with main (updated from main on 2 DEC, 2025)
• [ ] Ensure OPENEDX_COMMON_VERSION is pointing to correct tag release/ulmo.1

Merge Option

• [ ] Ensure "Merge Commit" option is used to merge the branch into release (Responsible: @ahmed-arb ). This is needed to ensure the commit history when release is merged back into main