gitea-ci: add zip to the CI image

Lambda packaging steps in some workflows shell out to `zip`; the image
only had `unzip`. Add `zip` alongside it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ansible/roles/gitea-actions/templates/Containerfile.ci

@@ -7,7 +7,7 @@ ARG DOCKER_CLI_VERSION=27.3.1
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         ca-certificates curl git openssh-client make build-essential \
-        python3 python3-pip jq unzip \
+        python3 python3-pip jq zip unzip \
     && rm -rf /var/lib/apt/lists/*
 
 # Static docker client (no daemon) for jobs that run `docker build` against the