fix: restore nightly release workflow structure

[vitormattos]

Summary

Repairs the nightly workflow after the release-note refactor was merged with a malformed shell block.

The corruption happened around the grep -v '^nightly$' expression and duplicated the release publication steps inside the shell block. This PR restores the intended workflow structure from the last known-good nightly template and reapplies the shared release-notes-from-pull-requests action cleanly.

Validation

Adds regression assertions that:

• the tag-selection command is present intact;
• the GitHub release creation step appears exactly once;
• the release asset upload step appears exactly once;
• the Nextcloud App Store upload step appears exactly once;
• the shared release-note action remains pinned to the immutable merged SHA;
• the old inline PR-resolution loop is absent.

Signed-off-by: Vitor Mattos vitor@php.rio