Add ARGS for USER and UID to all containers

Users should be able to run the containers as whatever user they want. We default to uid/gid 1000 which works for most use cases, but someone should be able to run as root if they want.

Inspect the repository's Dockerfiles to identify every container and how the default UID/GID and USER settings are currently defined. Determine the ARG-based changes needed across all containers, then verify that builds and runs accept custom user values, including root.

Written by the indexing model from the issue text.