Two fixes addressing architectural review feedback:
1. Snowflake ID collisions: Replace process.pid-based worker ID with a
cryptographically random value (0-1023) generated once at first boot
and persisted to instance_settings.worker_id. Eliminates deterministic
ID collisions between Docker instances that all run as PID 1.
2. Reaction API leak: Revert addReaction/removeReaction signatures to
(messageId, emoji) — the store now resolves the channel internally by
scanning its message cache, keeping routing logic out of the UI layer.
Jannis Braun