Validate port mappings for empty host ports, in-form duplicates,
privileged low ports, and peer-side host port conflicts. Runs on
template deploy, deploy view, and add-container before create RPC.
Adds a dedicated blank create form (name, image, always pull, ports,
auto-remove, advanced settings) separate from template Deploy, reuses
deployContainer with pull-if-missing and publish-all-ports support.
Raven Scott