Add docker-compose.local.yml for native arm64 dev builds

[paynejd]

Summary

• New opt-in docker-compose.local.yml that adds build: . to the api service so arm64 dev hosts (Apple Silicon, arm64 Linux) compile the image locally from python:3.12-slim instead of running the amd64 published image under Rosetta/QEMU
• README section documenting when to use it
• Production / CI behavior unchanged (base docker-compose.yml untouched)

Why

Closes OpenConceptLab/ocl_issues#2538. The published openconceptlab/oclapi2:production is amd64-only. On Apple Silicon under OrbStack / Docker Desktop, post-restart Celery indexing saturates emulated cores hard enough to block the API for 10–60s on most requests.

Measured on an M4 MacBook (24 GB):

Operation	amd64 emulated	arm64 native (this PR)
GET /orgs/	10s timeout	~20 ms
POST /concepts/	60s timeout	~280 ms

Discovered while standing up a local oclapi2 + FHIRsmith demo — without this fix the stack was effectively unusable on Apple Silicon.

Design notes

• Adds build: only on the api service; the other 8 services that share the openconceptlab/oclapi2:${ENVIRONMENT-production} image tag pick up the locally-tagged image automatically.
• Mirrors the existing opt-in pattern from docker-compose.sso.yml (invoked via -f) rather than re-introducing docker-compose.override.yml (which the repo previously took out of auto-load, now .bak).
• Docker compose will only build on first run — existing arm64 users with the amd64 image already cached can do a one-time docker compose -f docker-compose.yml -f docker-compose.local.yml build api (also called out in the README).

Test plan

• docker compose -f docker-compose.yml -f docker-compose.local.yml config parses cleanly; api shows the merged build: block
• First-time docker compose -f docker-compose.yml -f docker-compose.local.yml up -d on M4 builds image as arm64/linux (verified with docker image inspect)
• All 13 services come up healthy after native build; GET /orgs/, POST /concepts/, /fhir/metadata all serve in <300ms
• amd64 dev verifying that running with the override still does the right thing (cached image reused; no unnecessary rebuild)

Longer-term suggestion

Publishing multi-arch images via docker buildx --platform linux/amd64,linux/arm64 in CI would remove the need for this override entirely. Worth a separate ticket.

🤖 Generated with Claude Code