ci: pin Docker API version to 1.43 (podman compat)

Docker CLI v1.52 is too new for the host's podman daemon (max 1.43).
Set DOCKER_API_VERSION to force the older API.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -146,6 +146,7 @@ jobs:
     env:
       REGISTRY: ${{ env.GITEA_REGISTRY }}
       OWNER: ${{ env.GITEA_OWNER }}
+      DOCKER_API_VERSION: "1.43"
     steps:
       - uses: actions/checkout@v4