feat(billing): Seat purchasing for groups

[betimshahini]

Why

To expand the membership of groups (admin-only for now) beyond 3, we need to introduce seat-based purchasing options to allow organizations to fully manage costs and membership need.

What

Add ability to buy seats for groups, to be applied when membership size goes beyond the free 3 seats that we provide. This will be available in the Billing page, but only within a group context (not individual). Seats are purchased and assigned per group. Unassigned ones should be highlighted for the users on the groups page.

How

• UX design

[picassobanana]

Figma link

Preview:

Group Context

Billing&Purchasing Context

[betimshahini]

Work broken down into implementation items. Closing umbrella ticket.