Story: Slack Integration (US-5)

[yashrastogi]

As a workspace member, I want to connect my Slack workspace so that I can receive and respond to Slack messages without leaving Sentinent.

Acceptance Criteria

• User can authenticate with Slack via OAuth
• User can select channels to monitor
• Slack messages appear as signals in the dashboard
• User can mark Slack messages as read from Sentinent
• Rate limiting and error handling for Slack API

Technical Scope

Slack OAuth, webhook handlers, message storage, sync queue.