fix(compose): BUZZ_S3_ENDPOINT is hardcoded, so .env cannot point media at external S3

Start with deploy/compose/compose.yml:14 and compare its relay S3 environment with the settings documented in .env.example. Run the documented Docker Compose reproduction, checking the relay environment and upload destination with and without BUZZ_S3_ENDPOINT. Done means the .env value reaches the relay while an unset value still uses bundled MinIO.

Describe the bug

deploy/compose/compose.yml:14 hardcodes the S3 endpoint on the relay service:

BUZZ_S3_ENDPOINT: http://minio:9000

Every other S3 setting is env-driven and documented in .env.example — BUZZ_S3_ACCESS_KEY, BUZZ_S3_SECRET_KEY, BUZZ_S3_BUCKET, BUZZ_S3_ADDRESSING_STYLE — so setting BUZZ_S3_ENDPOINT there looks like it should work. It is silently ignored, and the relay keeps using the bundled MinIO.

The failure is quiet: the stack comes up, Media storage connected is logged, and uploads succeed — into MinIO on local disk rather than the configured bucket. Nothing indicates the endpoint was overridden.

This matters because the Helm chart directs production deployments the other way (deploy/charts/buzz/values.yaml):

Production: point endpoint/bucket at an external S3-compatible service and supply credentials. Quickstart (minio.enabled: true): the chart runs an in-cluster, eval-only MinIO.

So compose users following the same guidance get local MinIO regardless of what they configure.

Steps to reproduce

1. Set BUZZ_S3_ENDPOINT=https://<account>.r2.cloudflarestorage.com in deploy/compose/.env.
2. docker compose up -d.
3. docker exec <relay> printenv BUZZ_S3_ENDPOINT → http://minio:9000.
4. Uploads land in the bundled MinIO volume, not the configured bucket.

Expected behavior

BUZZ_S3_ENDPOINT honours .env like the other BUZZ_S3_* values, defaulting to the bundled MinIO when unset:

BUZZ_S3_ENDPOINT: ${BUZZ_S3_ENDPOINT:-http://minio:9000}

Ideally with the variable added to .env.example alongside the other S3 settings.

Version and platform

• Buzz version: relay ghcr.io/block/buzz:sha-63496cc; also present on main as of 2026-07-30
• OS: Ubuntu 24.04, Docker Compose

Logs / additional context

Workaround is a compose override that also has to reset the MinIO health dependency, since the relay depends_on it:

services:
  relay:
    environment:
      BUZZ_S3_ENDPOINT: ${BUZZ_S3_ENDPOINT:?}
    depends_on: !reset
      postgres: {condition: service_healthy}
      redis: {condition: service_healthy}
  minio: {profiles: ["disabled"]}
  minio-init: {profiles: ["disabled"]}

Possibly related to #3273 (hardcoded path-style S3 addressing), which is the same class of compose-level S3 config being fixed rather than configurable.