Add support for running with Podman alongside Docker

[nezhar]

Feature: Support Podman

Currently, vibepod-cli only supports Docker for container operations. We should also add support to run with Podman, allowing users who prefer or require Podman (especially on Linux-based systems) to use vibepod-cli seamlessly.

Rationale

• Podman is a popular alternative to Docker, with similar CLI and compatibility.
• Supporting Podman gives users more flexibility in their container runtime choice.
• Improves accessibility for environments where Docker is not available or recommended.

Proposed Implementation

• Add abstraction to container operations so either Docker or Podman can be used.
• Detect which container runtime is available, or allow user selection via a flag/config.
• Update relevant documentation and tests.

References

• Podman documentation
• Podman vs Docker comparison

Acceptance Criteria

• vibepod-cli can run with both Docker and Podman
• Clear documentation on how to select/runtime
• Automated tests for both runtimes

[nezhar]

Implemented in #26