feat(scripts): add jarvis-brain data migration script

- Full typed migration utility at scripts/migrate-brain.ts
- CLI flags: --brain-path, --workspace-id, --user-id, --apply
- Status/priority/domain mapping for brain -> Mosaic enums
- Dry-run validation report (counts, mapping issues, missing refs)
- Apply mode with Prisma inserts, idempotency via metadata.brainId
- Validates: 95 tasks, 106 projects, 13 domains, 0 parse issues

Refs: MS21-MIG-001

package.json

@@ -17,6 +17,7 @@
     "lint:fix": "turbo run lint:fix",
     "format": "prettier --write \"**/*.{ts,tsx,js,jsx,json,md}\"",
     "format:check": "prettier --check \"**/*.{ts,tsx,js,jsx,json,md}\"",
+    "migrate-brain": "pnpm --filter @mosaic/api exec node --import tsx ../../scripts/migrate-brain.ts",
     "test": "turbo run test",
     "test:watch": "turbo run test:watch",
     "test:coverage": "turbo run test:coverage",