feat(ha): leader-election via Redis lock + /ready endpoint (active/passive, off by default)
- app/leader: Elector (SETNX lock + PEXPIRE heartbeat via Lua, IsLeader)
- app/persistence: TryAcquireLock/RefreshLock/ReleaseLock (no-op when Redis absent)
- app/router: /ready -> 200 if ReadyFunc nil/true, else 503 (both planes)
- app/cmd: --leader-election / SHARED_SQS_LEADER_ELECTION, --leader-ttl, --leader-interval;
ReadyFunc wired only when enabled, lock released on graceful shutdown
- default OFF: single-instance behaviour unchanged
Repinoid
d7b3c653e0