ci: update workflows (#2041)

* ci: add/improve step names in workflows

Enhance workflows by adding and updating step names, improving log readability in CI runs.
Also removes `name` properties from jobs in `check-pr-title`, so they can be called by their identifiers.

* ci: refactor release workflow structure

* chore: update action dependencies

* ci: enhance container image build workflow

- Add concurrency control and job timeout to prevent redundant runs and hung workflows (e.g. on stuck AUR builds)
- Utilize Docker Buildx to provide an explicit BuildKit builder, rather than depending on whatever configuration the runner may have
- Keep immutable per-build tags so updating `latest` doesn't make previous images difficult to recover
- Use standard OCI image metadata labels for better traceability and versioning
- Enable pulling base images during the build process

* ci: downgrade nix-quick-install-action again

Pinned to v34 since other users have reported issues with it.

* ci: use shared action for nix flake updates