Implement FindContainerName method on DockerAPI that attempts exact match
first, then falls back to prefix-based matching (e.g., extracting prefix
before dash like "service-" in "service-abc") to replicate the old shell
script's `grep $D"-"` behavior. Update firewall orchestrator to use this
resolution before connecting containers to networks, improving robustness
when container names vary from configured selectors.
Downgrade the IP forwarding failure from an error to a warning,
as this is expected in containers with a read-only filesystem.
IP forwarding should be set at the host level, not inside a container.
Update comments to reflect this expectation and improve log clarity.
