[dashboard] Fix active state in usage-based billing account selector

[jankeromnes]

Description

Fix active state in usage-based billing account selector:

• When a team is selected, only show one team as active, not all teams (🤦)
• Align with workspace-start auto-selection logic (i.e. no user choice + only one billing team --> auto-select that one)

Related Issue(s)

Fixes https://github.com/gitpod-io/gitpod/issues/11962

How to test

1. Enable usage-based billing by creating a team called Gitpod [Something]
2. In /billing, no billing account should be selected
3. Upgrade team Gitpod [Something] to usage-based billing by adding a payment method (e.g. 4242 4242 4242 4242, 4/24, 424)
4. In /billing, that one team should now be auto-selected
5. Create and upgrade a second team called Gitpod [Something Else] to usage-based billing (you can add the same credit card as above)
6. In /billing, no billing account should be selected
7. If you manually select one team, it should show up as active (and all other options should remain inactive)

Release Notes

NONE

Documentation

Werft options:

• [x] /werft with-preview
• [x] /werft with-payment

[jankeromnes]

/werft run

:+1: started the job as gitpod-build-jx-active-billing-account.1 (with .werft/ from main)