langfuse: replace MinIO with SeaweedFS

[IgorTerenti]

Summary

minio is now archived and langfuse was the only thing in ODS using it (s3 store for event uploads). Swapped it for a single seaweedfs container running master + volume + filer + s3 gateway in one process. Creds come in via AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY, which seaweedfs turns into a static admin identity. Telemetry, IAM, iceberg, and lance listeners are off. Small init container creates the langfuse-events bucket with weed shell and is safe to re-run.

Also renamed the .env keys to LANGFUSE_S3_ACCESS_KEY / LANGFUSE_S3_SECRET_KEY across the linux/macos/windows env generators, schema, .env.example, and fixtures. Dropped four LANGFUSE_MINIO_* schema keys that nothing generated or consumed. Data dir moves to data/langfuse/seaweedfs, old minio data isn't migrated (different on-disk format).

Two commits: one functional, one NFC for docs/comments.

AI Assistance

Claude Code drafted the analysis, compose rewrite, and doc updates. I ran the validation below on real hardware and read the full diff.

Release Lane

• Stable hotfix targeting release/2.6.x
• Mainline change targeting main
• Next-minor work targeting the next feature/minor release
• Not sure; reviewer should help classify

Stable hotfix reason:

n/a

Changed Surface

• Docs only
• Tests only
• Dashboard UI
• Dashboard API / host agent
• Model routing / Hermes / capabilities
• Network exposure / auth / proxy
• Dependencies / runtime wiring

Risk And Validation

• Risk level: High
• Validation run:
  • git diff --check
  • Markdown/link sanity for docs
  • Focused tests listed below
  • Dashboard lint/test/build
  • Extension audit / compose validation
  • Release-grade fleet or scoped hardware validation
  • Stable-lane patch validation, if targeting release/2.6.x
  • Not required because:

Commands/results:

make lint                                          -> pass
make test                                          -> pass
make smoke                                         -> pass
python3 scripts/check-dependency-pins.py           -> pass
bash tests/contracts/test-installer-contracts.sh   -> pass
python3 scripts/audit-extensions.py --project-dir . langfuse -> clean
docker compose config (base + litellm + langfuse)  -> renders, no warnings

live stack (linux, nvidia):
  ods enable langfuse -> all six langfuse containers healthy, init Exited (0)
  s3 auth on: seaweedfs log shows admin identity added from env vars
  sent one request through litellm -> event landed under /buckets/langfuse-events/<project-id>
  no NoSuchBucket / InvalidAccessKeyId / SignatureDoesNotMatch in worker logs
  ods stop && ods start -> init re-ran and Exited (0), bucket data still there
  seaweedfs RSS ~60MiB against the 512MiB limit

Operational Change Check

• This is not an operational change.
• This is an operational change and validation is recorded above.
• This is an operational change and validation is intentionally deferred for:

Notes For Reviewers

• Anyone who already had langfuse enabled gets fresh s3 keys and an empty event store on next install run. Traces in clickhouse/postgres are unaffected. README has an "Upgrading from MinIO" note and the old data/langfuse/minio/ dir can just be deleted
• Image is chrislusf/seaweedfs:4.47. There's no seaweedfs/seaweedfs on docker hub, upstream publishes under the maintainer's account (mirrored from ghcr). Happy to switch to the ghcr path if you'd rather avoid hub pull limits
• Kept the init container even though seaweedfs auto-creates buckets for admin identities. Deterministic beats "probably works" here IMO
• Memory limit went 256m -> 512m since one process now runs four components. Actual usage is way under
• tests/smoke/installer-env-smoke.sh has two pre-existing failures (undefined ai_err), unrelated to this change
• Noticed lib/backup-paths.sh skips all of data/langfuse/* and the coverage test never scans compose.yaml.disabled. Pre-existing gap, left it out of this PR to keep it one concern. Can open an issue if wanted

Assumed venue: PR description, so I kept the repo's required template sections and filled them in the review register.