Creates a ThinkLP investigation case and atomically links a batch of Frontier point-of-sale transactions to it as snapshots. Each transaction's employee is resolved to a canonical Person and attached as an involved person (unresolved employees are skipped and counted); each line item is provisioned as a canonical Item and attached as a case item, aggregated case-insensitively by SKU. The whole operation is transactional: any failure rolls back the case and every link.