Fix image builds for tags

[hk60418]

Overview

Currently, multi-platform (ARM64/AMD64) Docker images are only built for latest because the container workflow doesn't trigger on tag pushes. This PR adds a tag trigger so that release versions (e.g., 0.23.0) also receive multi-platform manifests. Without tagged ARM64 images, developers on Apple Silicon Macs cannot use specific versions and must either build locally or rely on latest, causing friction in development workflows.

Related Issue / discussion

Could not find a PR relevant for this feature.

Additional information

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute feature/bugfix to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution

I agree to the pygeoapi Contributions and Licensing Guidelines.

• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[tomkralidis]

@hk60418 in the future, as mentioned by the PR template, please open an issue for discussion and consensus.