Move the workflow actions onto their Node 24 majors

[basecubedev]

Five actions released a major at once, and all five majors are the same change: the action's own runtime moves from Node 20 to Node 24. GitHub is deprecating Node 20 on its runners, so this is the direction the pins have to go anyway, and ubuntu-latest already runs a runner new enough for it.

What the release notes call breaking, checked against what these workflows actually pass:

• setup-buildx-action v4 drops its deprecated inputs. Both call sites use the action bare, with no with: block at all.
• metadata-action v6 changes how # is read inside a list input: it now survives in a value and only starts a comment on its own line. Neither the tags: nor the labels: list here contains one.
• login-action v4 and action-gh-release v3 are the runtime bump alone; the inputs used here -- registry, username, password, and draft, prerelease, files, body -- are untouched.
• setup-uv v7 additionally stops overwriting UV_CACHE_DIR when the workflow already set it, which ci.yml does, and warns instead. That is the behaviour the workflow wanted in the first place.

Only the setup-uv pin sits in ci.yml, so it is the only one a pull request proves. The other four live in edge.yml and release.yml, which run on a push to main and on a v* tag and never on a pull request -- a green check on this change says nothing about them, and the first real evidence is the next edge build.