fix(ci): use semver-compatible version string for Gitea image

Change GITEA_VERSION from 'neuron-<sha>' to '1.26.1-neuron.<sha>' so
tea and other clients that parse the version can correctly identify it
as 1.26.1-compatible and enable the full API surface.

.gitea/workflows/build-push.yaml

@@ -82,7 +82,7 @@ jobs:
           done
           docker buildx build \
             --load \
-            --build-arg GITEA_VERSION="neuron-$(git rev-parse --short HEAD)" \
+            --build-arg GITEA_VERSION="1.26.1-neuron.$(git rev-parse --short HEAD)" \
             --build-arg TAGS="sqlite sqlite_unlock_notify" \
             $TAGS \
             .