feat: Coinflow Credits Flow (#471)

Co-authored-by: Derek <256792747+decofe@users.noreply.github.com>
Co-authored-by: Amp <amp@ampcode.com>

Author: 3 people

.changelog/coinflow-credits.md

@@ -0,0 +1,6 @@
+---
+tempo-common: minor
+tempo-wallet: minor
+---
+
+Add wallet CLI support for checking and spending Coinflow credits, and update shared signer handling so wallet flows can emit the expected Tempo signature format for these transactions.