Script for docker entrypoint and documentations

[chetanr25]

Add docker entrypoint, README, and thin top-level docker-compose.yml

Context

Final piece of the docker reorganization. Once dev and prod live under docker/, we need the shared glue and a default entrypoint so contributors run one obvious command.

Goal

docker/
  entrypoint.sh    # shared container entrypoint
  README.md        # which compose file to use when
docker-compose.yml # thin top-level, defaults to docker/dev

Tasks

• docker/entrypoint.sh: replaces the current container-init.sh; handles container startup (wait for deps, DB init, launch command). Used by dev and prod Dockerfiles.
• docker/README.md: short table which file for dev, prod, and any extra/admin compose; one-line purpose each.
• Root docker-compose.yml: thin file that delegates to / includes docker/dev/compose.yml so a bare docker compose up gives the dev environment.
• Remove the old root Dockerfile and container-init.sh once superseded.

Depends on

• docker/dev/ Add Docker dev environment #514 and docker/prod/ Add docker prod environment #515 issues.

Part of #512