Create GET /api/dashboard/summary aggregating 10 parallel Prisma
queries: task metrics, active agents, project counts, error rate,
recent activity, active runner jobs with steps, token budget entries.
Guarded by AuthGuard + WorkspaceGuard + PermissionGuard.
Includes DTO classes and unit tests.
Task: MS-P2-001
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
