Maayan via Elementary: Add upstream tests for cpa_and_roas pipeline

[joostboon]

Upstream Test Coverage for cpa_and_roas

Adds volume and freshness anomaly tests to staging models that feed into the cpa_and_roas pipeline:

stg_orders (5-level upstream)

• Volume anomaly — Detects sudden drops or spikes in row count that would cascade through real_time_orders → orders → cpa_and_roas
• Freshness anomaly — Ensures the staging layer receives timely updates to keep the real-time pipeline current

stg_payments (5-level upstream)

• Volume anomaly — Missing payment records would cause zero-value amounts, distorting ROAS figures
• Freshness anomaly — Stale payment data leads to incomplete monetary calculations downstream
  
  Created by: maayan+172@elementary-data.com