Connect messaging channels

Customer: Where is my order #12345?
Agent: Looks up order in iCommerce → returns status and tracking.

# One channel
stateset-whatsapp --db ./store.db

# Every channel marked enabled in channels.json
stateset-channels --db ./store.db

{
  "whatsapp": { "enabled": true, "phone_number_id": "xxx", "access_token": "xxx" },
  "slack":    { "enabled": true, "bot_token": "xxx", "app_token": "xxx" },
  "discord":  { "enabled": false, "bot_token": "xxx", "guild_id": "xxx" }
}