fix(docker): remove invalid {{is_tag}} enable expr — latest always added

[argszero]

Summary

Fix docker-publish failure on the v0.7.6 tag: enable={{is_tag}} is not a valid expression in docker/metadata-action v5 — the action threw Invalid value for enable attribute: and the whole release job failed.

Since the workflow now triggers only on tags: ['v*'] (PR #116, plus workflow_dispatch), the latest tag can simply always be added — it will only ever be refreshed by a version tag push (or an explicit manual dispatch), which is exactly the intended tag-driven release cadence.

Changes

• .github/workflows/docker-publish.yml: type=raw,value=latest,enable={{is_tag}} → type=raw,value=latest

Tests

• Workflow-only change (no Rust/JS code touched); YAML validated
• Fix will be exercised by re-pushing the v0.7.6 tag after merge (the tag will point to the merge commit containing this fix, since Actions runs the workflow file from the triggering ref)