ci(release): trigger docker build via workflow_dispatch

[raaymax]

Summary

Fixes the release workflow, which startup_failured on the v3.5.1 release (PR #295) — the GitHub Release and image build never ran.

Root cause

The docker: job added to release.yml called docker.yml as a reusable workflow (uses: ./.github/workflows/docker.yml) from a pull_request-triggered workflow. v3.5.1 was the first release to exercise it, and that call fails workflow validation at startup (the whole run dies in ~1s with zero jobs and no usable error — GitHub only reports "workflow file issue"). The previous v3.5.0 release predated this job and ran fine.

Fix

Replace the reusable-workflow call with an explicit workflow_dispatch of docker.yml:

• release.yml: after creating the Release, dispatch docker.yml on main with the version via actions/github-script (createWorkflowDispatch). Adds actions: write permission (required to dispatch) and drops the now-unused outputs/docker reusable job.
• docker.yml: add an optional version input to workflow_dispatch so the dispatched build tags the image correctly (APP_VERSION / image tag already fall back to github.ref_name).

This avoids the fragile reusable-call-from-pull_request pattern. A token-created release/tag does not trigger on: push: tags, so the explicit dispatch is the reliable chain.

Note

v3.5.1 was recovered manually (tag pushed → image built & published, Release created). This fix takes effect from the next release.