fix(ci): pull pinned MinIO images from Quay (#7599)

## Summary

CI is failing in `main` before tests start because Docker Hub denies
pulls for `minio/minio` and `minio/mc`. Retrying the failed jobs
produced the same errors.

Use MinIO’s Quay images in the development, harness, deployment Compose,
and Helm configurations. Pin each image to its multi-platform digest and
retain the release tags already used by deployment templates. Update the
architecture reference to match.

### Related issue

No duplicate issue or PR found. Addresses the image-pull failures in
[main CI attempt
2](https://github.com/block/buzz/actions/runs/34645306855/attempts/2).

### Testing

- Pulled both pinned images for Linux ARM64 and AMD64.
- Started an isolated Compose stack derived from the updated MinIO
service definitions, once per architecture (AMD64 under local
emulation).
- Verified the existing health check passed and the bucket initializer
exited with code 0.
- Uploaded an object with `mc cp`, read it with `mc cat`, compared its
content, and deleted it with `mc rm` on both architectures.
- Confirmed the initialized bucket was private and removed the temporary
stack and volume.

Generated with Codex

Signed-off-by: Salman Mohammed <smohammed@squareup.com>

ARCHITECTURE.md

@@ -783,7 +783,7 @@ Docker Compose provides the full local development stack. All services include h
 | Postgres | `postgres:17-alpine` | 5432 | Primary event store — events, channels, tokens, workflows, audit; full-text search (`search_tsv` GIN) |
 | Redis | `redis:7-alpine` | 6379 | Pub/sub fan-out, presence (SET EX), typing (sorted sets) |
 | Adminer | `adminer` | 8082 | DB web UI (dev only) |
-| MinIO | `minio/minio` | 9000 (API), 9001 (console) | S3-compatible object storage (media) |
+| MinIO | `quay.io/minio/minio` | 9000 (API), 9001 (console) | S3-compatible object storage (media) |
 | Prometheus | `prom/prometheus` | 9090 | Metrics collection |
 
 ### Postgres Schema (key tables)