fix: default payment methods

[fetchfern]

• If a default payment method doesn't exist explicitly on Stripe's end, use the customer's payment method if only one exists. Retrying across multiple payment methods will be implemented later.
• The frontend currently assumes that the first payment method is the primary, if no explicit primary exists. Fix this to reflect the new behavior.

Fixes DEV-1472

[github-actions]

Pull request changelog

App

Added

Changed

Deprecated

Removed

Fixed

Security

Website

Added

Changed

Deprecated

Removed

Fixed

Security

Hosting

Added

Changed

Deprecated

Removed

Fixed

Security

[github-actions]

Frontend previews

Last deployed commit is 1a9aed74b28b1692d7edfeaf2d864e959700183c

Persistent

Environment	URL
staging	https://pr-7823-staging-frontend.modrinth.workers.dev
production	https://pr-7823-frontend.modrinth.workers.dev
storybook	https://pr-7823-storybook.modrinth.workers.dev

Latest commit

Environment	URL
staging	https://git-1a9aed74-staging-frontend.modrinth.workers.dev
production	https://git-1a9aed74-frontend.modrinth.workers.dev
storybook	https://git-1a9aed74-storybook.modrinth.workers.dev

[mergify]

Queued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-10-06 16:28 UTC · Rule: default · triggered by @fetchfern with the merge queue checkbox
• 🚫 Left the queue — 2026-10-06 16:55 UTC · at 61cc0645ba04f44b826be0671a68b20029b1a927

This pull request spent 26 minutes 43 seconds in the queue, with no time running CI.

Reason

Pull request #7823 has been dequeued

Queue conditions are not satisfied:

• -conflict [📌 queue requirement]

Hint

You should look at the reason for the failure and decide if the pull request needs to be fixed or if you want to requeue it.
If you do update this pull request, it will automatically be requeued once the queue conditions match again.
If you think this was a flaky issue instead, you can requeue the pull request, without updating it, by posting a @mergifyio queue comment.

Requeued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-10-06 20:03 UTC · Rule: default · triggered by @fetchfern with the merge queue checkbox
• ✅ Checks passed · on draft merge queue: checking #7823 on main (e21f0ff) #7867
• ✅ Merged — 2026-10-06 20:19 UTC · at ed5ccb5f4576a9924f3958d071e5da8dc7d13a3a

This pull request spent 16 minutes 13 seconds in the queue, including 15 minutes 45 seconds running CI.

Required conditions to merge

• github-review-approved [🛡 GitHub branch protection]
  • fix: default payment methods #7823
• any of [🛡 GitHub branch protection]:
  • check-success = Lint and Test
  • check-neutral = Lint and Test
  • check-skipped = Lint and Test