Show the customer's local time on payment timestamps

The timestamp tooltip in the dashboard currently shows four lines: the merchant's timezone, UTC, relative time, and the raw epoch. It shows nothing about the customer's local time.

Support teams need this to judge when a payment or failed renewal happened from the customer's side, and to time follow-ups.

Example from the merchant's dashboard: a payment where the merchant sees 23 Oct, 2:20 AM (Asia/Calcutta) while the customer's local time was 22 Oct, 10:50 PM. A different calendar day, which is exactly the confusion that makes support harder.

Current limitation

We do not capture the customer's timezone anywhere today. The billing address is the closest signal we hold, but it is unreliable for countries spanning multiple timezones, and the billing address is not necessarily where the customer actually is.

Proposed

1. Capture the browser timezone at checkout
2. Store it against the customer
3. Add the customer's local time as an extra line in the existing timestamp tooltip, alongside the merchant timezone, UTC and relative time

Requested by Atlabs, 23 Oct 2026.