ci(release): skip homebrew-tap publish on forks (#1687)

The release job uses GoReleaser to bump the formula in
multica-ai/homebrew-tap. Forks don't have HOMEBREW_TAP_GITHUB_TOKEN
and should not publish to that tap, so the job currently fails on
every fork tag push (401 Bad credentials against the upstream tap).
This makes the workflow red on downstream forks even though the
actual artifact pipeline (verify → docker-backend-build →
docker-backend-merge) succeeds and produces a usable image.

Gate the release job on `github.repository_owner == 'multica-ai'`.
Upstream behaviour unchanged. Forks now see a clean green run for
docker artifacts only.

.github/workflows/release.yml

@@ -56,6 +56,12 @@ jobs:
 
   release:
     needs: verify
+    # Only run on the canonical upstream repo. Forks don't have the
+    # HOMEBREW_TAP_GITHUB_TOKEN secret and should not be publishing to
+    # `multica-ai/homebrew-tap` anyway. Without this guard, every fork's
+    # tag push fails this job (401 against the upstream tap), which makes
+    # downstream CI go red without affecting the actual artifact pipeline.
+    if: github.repository_owner == 'multica-ai'
     runs-on: ubuntu-latest
     steps:
       - name: Checkout