- Create brain module with service, controller, and DTOs - POST /api/brain/query - Structured queries for tasks, events, projects - GET /api/brain/context - Get current workspace context for agents - GET /api/brain/search - Search across all entities - Support filters: status, priority, date ranges, assignee, etc. - 41 tests covering service (27) and controller (14) - Integrated with AuthGuard, WorkspaceGuard, PermissionGuard