Allow workspace members to use their own credits

Currently, all credits in a workspace are pooled together and consumed from the workspace owner's plan. I'd like the ability for individual workspace members (e.g. engineers, collaborators) to connect their own paid Base44 plan and have their edits/prompts consume credits from their own account rather than the workspace pool.

This would be especially useful when bringing on external contributors or contractors who want to pay for their own usage without relying on the workspace owner's credit balance. It would make collaboration more scalable and flexible for teams of all sizes.