FluentCart integrations and background jobs

Choose between an integration feed, a direct lifecycle listener, and an addon-owned job based on configurability and durability. Every external side effect must tolerate delayed delivery, duplicate delivery, and partial failure.

Read integration-queue-map.md before adding a provider or diagnosing the queue.

Use the feed framework for configurable providers

Extend BaseIntegrationManager when store administrators need global/product feeds, event selection, conditional routing, provider credentials, smartcodes, priority, and background execution. Register the manager after FluentCart has loaded and implement: