chore: bump Synapse to 1.155.0; 1.154.0:0 → 1.155.0:0

[helix-nine]

Summary

Bumps Synapse 1.154.0 → 1.155.0 (minor; bugfixes only). Ketesa (admin dashboard) stays at v1.2.1 — no upstream movement. @start9labs/start-sdk already pins the latest (1.5.3); npm update refreshed transitive deps in package-lock.json.

Changes

• dockerTag → ghcr.io/element-hq/synapse:v1.155.0 in startos/manifest/index.ts.
• startos/versions/current.ts: version → 1.155.0:0, release notes updated in all locales. Edited in place (no new migration); the existing idempotent clearTask migration is carried forward, matching the prior bump.

Upstream highlights (1.155.0)

• Limit to-device EDU size to keep outgoing federation from stalling.
• Work around a failure when joining restricted rooms requiring a remote join.
• Sliding Sync returns updated room subscriptions immediately.
• Last Synapse release to ship Debian 12 Bookworm packages (does not affect this StartOS package).

Full notes: https://github.com/element-hq/synapse/releases/tag/v1.155.0

Test plan

• npm run check (tsc --noEmit) — green.
• make / s9pk build verification deferred to PR review per monitor-cycle policy.

[helix-nine]

Thanks for the review and merge, @MattDHill! Synapse 1.155.0 is in. 🚀