Sliding-window rate limiter (30 req/min per peer origin) on POST
/api/federation/relay, matching the existing accept endpoint pattern.
Returns 429 when exceeded — outbox workers retry with backoff. Check
runs before HMAC verification to avoid wasted computation on floods.
Extract processRelayEvents() from the relay HTTP handler and call it
directly in runInitialSyncForNewPeers(), eliminating the HTTP round-trip
through public DNS that failed on networks without hairpin NAT.
Comprehensive internal document covering the complete lifecycle of
federated DMs: data model, relay pipeline, event processing, bootstrap
path, local-only broadcast principle, system messages, and all known
pitfalls with their fixes.