chore: release v1.21.0-beta.5

[Soju06]

Summary

• Prepares beta release v1.21.0-beta.5 for the 1.21.0 stable train.
• Updates release-managed version files only; release-please remains the stable release owner.
• Merging this PR will publish v1.21.0-beta.5 only after the release-candidate validation checklist below is completed for this exact candidate SHA.
• Synced automatically from release-please PR chore(main): release 1.21.0 #1087; no manual beta workflow dispatch is required.

Changes since v1.21.0-beta.4

• fix(accounts): serialize cross-replica token refresh with per-account DB claims (fix(accounts): serialize cross-replica token refresh with per-account DB claims #1254) (b5f0541)

Release-candidate validation

Validated candidate: e81e583

Complete these checks on the exact candidate SHA above before merging. The beta release guard and publish workflow fail while any item remains unchecked or the SHA is stale.

• Backend/unit/integration gates
• Frontend tests/build
• Wheel/package validation
• Docker/container smoke
• Live upstream/account smoke
• Live upstream/account smoke not required

Install after publish

uvx --from "codex-lb==1.21.0b5" codex-lb
docker pull ghcr.io/Soju06/codex-lb:1.21.0-beta.5
helm install codex-lb oci://ghcr.io/soju06/charts/codex-lb --version 1.21.0-beta.5 --devel

Promotion

Merge the normal release-please PR to promote this beta-tested train to 1.21.0.

[Soju06]

Superseded by the current beta release train v1.21.1-beta.1 from release-please PR #1330. Closing this automation-managed beta PR to avoid publishing an obsolete train.