fix(ci): pin the docker reusable past the syntax fix

[BryanFRD]

The Dockerfile fix in #84 was only half the story: the shared build script itself did not parse, so v0.24.1 still failed with syntax error: unexpected end of file. That is repaired in .github#257; this moves the pin onto it.

Only docker.yml is repinned. The other reusables in this repo stay where they are — the same range carries a FerrFlow action bump that belongs to a deliberate decision about the release flow, not to unbreaking an image build.

Once this lands, the release it cuts is the first version since 0.20.0 to actually produce a container.

0.21.0 through 0.24.0 stay imageless. Their tags contain the Dockerfile that trips hadolint on SC2155, so rebuilding them means rewriting released tags. They are superseded by the version this PR produces, and the chart's appVersion should simply never point at them.

[Copilot]

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[ferrfleet]

Clean, minimal pin bump: same new SHA applied consistently to both the build and verify jobs referencing reusable-docker-build.yml. Scope matches the description (only docker.yml touched, other reusables intentionally left alone). Nothing blocking.

[github-actions]

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