Fix review findings for info broker removal service FRE-5402

P0 fixes:
- Add CANCELLED status to RemovalStatus enum (types + Prisma schema)
- Use CANCELLED instead of REJECTED for user-initiated cancellations
- Add null guard for req.broker?.name in GET /request/:id
- Remove unsafe 'as any' casts in RemoveBrokersService.ts
- Add type-safe toPersonalInfo() validator for JSON deserialization
- Type RemovalRequestWithBroker properly in getRemovalStatus()
- Fix alert: any to NormalizedAlertInput in BrokerAlertPipeline

P1 fixes:
- Fix admin role check: remove non-existent 'admin', only check 'support'
- Fix BrokerDefinition.category type from string to BrokerCategory
- Add complete OpenAPI spec for all removebrokers routes and schemas

packages/db/prisma/schema.prisma

@@ -838,6 +838,7 @@ enum RemovalStatus {
   COMPLETED
   FAILED
   REJECTED
+  CANCELLED
 }
 
 model InfoBroker {