fix_timer_bug

[pory-gone]

Description

Fixed #2646

QR code payment status timer was stuck at 00:00, the cause was a timezone interpretation bug. GraphQL Date scalar returns ISO 8601 strings without the 'Z' UTC suffix (e.g., "2025-11-21T12:31:08"), causing browsers to interpret them as local time instead of UTC. This made invoices appear expired immediately in non-UTC timezones. This fix adds 'Z' to expiresAt timestamps when missing.

Screenshots

after.mp4

Additional Context

Also fixed a shadow variable bug in cancelAndReject that prevented proper state updates. added polling with FAST_POLL_INTERVAL_MS to keep payment status updated.

Checklist

Are your changes backward compatible? Please answer below:
Yes

On a scale of 1-10 how well and how have you QA'd this change and any features it might affect? Please answer below:
8/10

For frontend changes: Tested on mobile, light and dark mode? Please answer below:
nan

Did you introduce any new environment variables? If so, call them out explicitly here:
nan

Did you use AI for this? If so, how much did it assist you?
I used AI to create a strategy to catch and understand the bug to apply the correct changes

[huumn]

Thank you for identifying the issue! For raw queries, we return timestamp fields as strings which are often stored without time zones, and the serialization of Date scalar would simply pass along the string. The solution, I think, is to always add a time zone on serialization.

I'll create an award for your work.