Badge purchases and refunds during event

[marksteward]

This is going to be be useful because badges are typically in high demand. We should add a per-purchase refund button (or at least expose which payments are which on the accounts page), and allow unredeemed badges to be refunded at any time, ignoring the main refund state (maybe with a new state). And then either automatically approve badge refunds or a new permission that allows the badge team to deal with them. This new permission should probably also allow refunding directly.

Badges and batteries should also be purchasable at any point, if we have them, potentially behind a voucher code. The voucher code should be issuable by the badge admin, to allow them to trickle out badges as they become available.