Proxy /exchange/applications, without the consumption flag

Forwards an application to become a provider. Every other route here is gated
on exchangeRetrieve, which is what grants consuming the Exchange; an applicant
is not yet a customer of anything, so gating this on it would refuse exactly
the people the route exists for.

The flag stays required by default and is opted out of once, here, rather than
being a parameter each route remembers to pass.

Claude-Session: https://claude.ai/code/session_01KpbshKPNuCDBD4TLJ8T2UQ