Follow-on to correct #1009. The previous fix downgraded upload-artifact
to v3 but kept download-artifact@v4, creating incompatible storage
formats that prevented artifact pattern filtering from working.
Update all upload-artifact actions to v4 and adjust renovate
configuration to disable automatic updates for forgejo artifact
actions to maintain version consistency.
Resolve upload-artifact v4 GHES compatibility errors by downgrading to v3.
Switch to standard forgejo/download-artifact@v4 for pattern filtering support.
Update renovate configuration to prevent future incompatible upgrades.
Add diagnostic output to digest export step to troubleshoot zero-byte
artifact uploads preventing manifest creation. Include CI triggers for
Element workflow to test changes in pull requests.
