ci(release): dispatch the fallback build with a fully qualified ref

Gitea's workflow dispatch API 404s on a bare `v1.0.3` and accepts only
`refs/tags/v1.0.3`, so the fallback added in fdbe9fd would have failed
the release instead of rescuing it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -223,8 +223,9 @@ jobs:
                   method: "POST",
                   headers: { ...headers, "Content-Type": "application/json" },
                   // Must be the tag, not master: metadata-action only emits the
-                  // X.Y.Z and X.Y image tags when the ref is a semver tag.
-                  body: JSON.stringify({ ref: tag }),
+                  // X.Y.Z and X.Y image tags when the ref is a semver tag. And
+                  // it must be the fully qualified ref — Gitea 404s on `v1.0.3`.
+                  body: JSON.stringify({ ref: `refs/tags/${tag}` }),
                 },
               );
               if (!res.ok) console.log(`Dispatch returned HTTP ${res.status}.`);