Standardize container instructions on the docker command (podman-docker)

[adamlam2-amd]

Playbooks previously mixed podman and docker commands, which caused friction for users who had one engine but not the other (surfaced by a user hitting podman-specific steps in the Hermes playbook).

Approach: all container instructions now use the docker command, which works with either real Docker or podman-docker (a wrapper that provides a docker-compatible CLI backed by the Podman engine, available in the Ubuntu repos). This means users need one of: Docker (if already installed), or podman-docker (which pulls in the Podman engine automatically). podman-docker is already preinstalled on HaloBox Linux.

Changes:

• dependencies/podman.md (shared container dependency): install simplified to sudo apt install -y podman-docker podman-compose; verify/run steps use docker / docker compose; added guidance that if you already have Docker you should use it and not install podman.
• User-facing instructions converted podman → docker in: n8n, open-webui, clustering-rccl, deepseek (install → podman-docker).
• CI test blocks updated to match the READMEs exactly (docker compose, docker exec/ps/logs, etc.); removed the now-unneeded PODMAN_COMPOSE_PROVIDER shim.
• Hermes & openclaw: converted HERMES_DOCKER_BINARY and systemd ExecStart* to /usr/bin/docker, and docker build/pull/compose/exec throughout. Windows paths run inside WSL, so podman-docker + docker apply there too. Also fixed two pre-existing bugs in Hermes along the way (stray backtick in the install command, and a malformed ExecStartPre missing the compose subcommand).
• Retitled the registry entry from "Podman" to "Container Engine (Docker/Podman)".

Intentionally unchanged:

• podman.socket/podman.service systemd unit names, the podman-docker/podman-compose package names, the @require:podman dependency id, and docker.io/... registry paths.

Requires:

• CI runners (and non-HaloBox target machines) to have podman-docker installed so docker / /usr/bin/docker resolve.

Known follow-up (not in this PR):

• OpenClaw's prerequisites still reference Docker Desktop for its optional sandbox — left as-is since it's optional and functional; can be reframed to podman-docker later.