Replace CI bash loop with Makefile

[loks0n]

Summary

• The bash arg-extraction loop introduced in Templated Dockerfile + slim runtime image #11 for sourcing versions/<X.Y>.env and turning each key into a --build-arg flag was hard to read and not reusable locally.
• Replace with a small Makefile exposing make build, make test, and make all.
• ci.yml now calls make build VERSION=… IMAGE=utopia-base-test instead of inlining shell.
• README updated to document the make targets.

Stacked on top of #11 — please review/merge that one first.

Test plan

• CI builds all three versions × both arches green via make build
• make test VERSION=8.4 passes locally with container-structure-test installed

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

Replaces the verbose bash arg-extraction loop in ci.yml with a small Makefile that exposes build, test, all, and clean targets, and updates the README accordingly.

• The awk-based BUILD_ARGS expansion and set -a env sourcing in the build target faithfully replicate the original shell logic; the CI change is a one-liner that delegates to make build.
• The VERSIONS list is auto-discovered via $(wildcard versions/*.env), avoiding the static hardcoding concern raised in prior review threads.

Confidence Score: 5/5

Safe to merge — the change is a straightforward refactor of CI shell logic into a Makefile with no behavioral changes to the build or test pipeline.

The Makefile faithfully replicates the original bash loop (env sourcing + awk arg extraction), the CI workflow change is minimal, and all downstream jobs remain unmodified.

No files require special attention.

Important Files Changed

Filename	Overview
.github/workflows/ci.yml	Build step simplified from a 10-line bash loop to a single make build call; downstream jobs (structure-test, dive, trivy) are unchanged and still reference utopia-base-test consistently.
Makefile	New Makefile exposes build/test/all/clean targets; awk-based BUILD_ARGS extraction and env sourcing faithfully replicate the original bash loop; version list is auto-discovered via wildcard so all avoids the hardcoded duplication concern.
README.md	Local-development section replaced with the three make targets; the note about adding new versions still correctly points to both ci.yml and publish.yml.

_{Reviews (3): Last reviewed commit: "Address PR feedback: derive versions lis..." | Re-trigger Greptile}