DRAFT: Improve DX: setup script for submodule and image syncing

[aprilrieger]

TO-DO

• Update the build to use the base_image as well

Update to add bin/setup for submodule initialization and BASE_IMAGE automation

Story

As a developer working on a HykuKnapsack project,
I want a single setup script that initializes the Hyku submodule and automatically sets the correct BASE_IMAGE,
So that I can start coding immediately without having to manually manage submodule state or rebuild Docker layers unnecessarily.

Refs #<issue_number>

Expected Behavior Before Changes

• Developers had to manually run multiple setup steps when starting work:
  • Initialize the hyrax-webapp submodule
  • Manually determine the correct SHA and update .env with the appropriate BASE_IMAGE
• If the submodule SHA changed (e.g., via git checkout), the .env file would not be updated automatically
• Builds could use outdated base images or default to :latest, which could lead to unnecessary rebuilds and slower startup times

Expected Behavior After Changes

• Running ./bin/setup will:
  • Automatically initialize the hyrax-webapp submodule (if not already)
  • Set the BASE_IMAGE in .env to match the currently checked-out commit in the submodule
  • Install a post-checkout git hook to keep BASE_IMAGE updated when switching branches
• Ensures the correct base image is used:
  • Matches the SHA of the hyrax-webapp submodule
  • Leverages Docker layer caching more effectively
  • Speeds up local development and reduces build inconsistencies