chore: rename qreleaser type "release" to "stable"

[donatello]

Summary

• Rename the qreleaser release type from release to stable to match
  the updated qreleaser v2 toolkit
• Convert .qreleaser.yml containers from old format to new array format
  with explicit rolling_tags: {stable: latest} and edge_enabled: false
  (this repo does not do edge releases)
• Update CI workflow to use stable as the default type, with a
  type_dir output that maps stable → release for artifact paths
  (the on-disk directory name is unchanged)

Context

The qreleaser toolkit renamed the internal release type to avoid
confusion with the overloaded word "release". All external artifacts
are unchanged — version tags still use RELEASE. prefix, dl.min.io
paths still use release/, and container rolling tags are unaffected.

Test plan

• CI workflow passes on this branch (qreleaser-test)
• Verify artifact paths resolve correctly (stable type → release/ dir)