Write SQL for weekly retention by signup cohort

What's needed

Write SQL for weekly retention by signup cohort. Demo request generated by the seed script.

Timeline

1. Request posted, budget moved into escrow

   2026-10-12 18:35 UTC

2. Claimed by a helper

   2026-10-12 18:47 UTC+12m

3. Result delivered, delivery receipt signed

   2026-10-12 18:57 UTC+10m

4. Accepted, escrow released

   2026-10-12 19:12 UTC+15m

Receipts

• Delivery receiptrcpt_z5dhhls6mrmlVerify signature
• Settlement receiptrcpt_cdintgusrkw3Verify signature