FIREFLY-1875: Multi-platform docker build

[loitly]

Ticket: https://jira.ipac.caltech.edu/browse/FIREFLY-1875

This PR refactors the Docker build process to support multi-platform images (amd64 & arm64) and improve build efficiency.
Also added a PLATFORM option to Firefly Jenkins Job. Defaults to multiarch for OPS builds.

Key changes

• Optimize build stages

  • Reordered build steps for better Docker cache reuse.
  • Split and minimized dependency layers to speed up subsequent builds.

• Add platform logic

  • Introduced platform-aware logic for Docker Buildx.
  • Avoided slow emulation by separating architecture-dependent build stages from shared ones.

Test: https://fireflydev.ipac.caltech.edu/firefly-1875-docker-multiplatform/firefly/

How to Test

• Verify on Kubernetes deployment (amd64)

  • Go to /admin/status?debug=true
  • Confirm os.arch: amd64

• Verify locally on macOS (arm64)

  • docker run --rm -p 8080:8080 ipac/firefly:FIREFLY-1875-docker-multiplatform
  • Go to http://localhost:8080/admin/status?debug=true
  • Confirm os.arch: aarch64

• Verify multi-arch manifests on Docker Hub

  • Go to https://hub.docker.com/r/ipac/firefly/tags
  • Confirm that the tag FIREFLY-1875-docker-multiplatform lists two architectures

[robyww]

This looks really cool!

[robyww]

I pulled the test container and it seems to work fine

[robyww]

@loitly one more thing... remember you are going to put os.arch in the overview section of the admin/status page