Admin dashboard shows Routstr provider Cashu balances as USD instead of sats

[shroominic]

Summary

When a new upstream provider is configured as a Routstr node and the upstream API key is funded with a Cashu token denominated in sats, the admin dashboard displays the provider balance as USD.

Steps to reproduce

1. Open the admin dashboard on the upstream providers page.
2. Add a new provider with type routstr.
3. Create or attach an upstream API key funded via a Cashu token in sats.
4. Return to the provider card and inspect the balance button.

Actual behavior

The UI formats the balance as USD, which makes the displayed number appear far too large.

Expected behavior

Routstr node balances should be shown in sats, matching the backend response and the upstream wallet unit.

Notes

The backend balance endpoint already returns Routstr balances in sats. The bug is in the shared provider balance UI, which was formatting all numeric balances as dollars and was not being told when the provider type was routstr.