feat(ffi): expose mint_unissued_quotes

[j-kon]

Summary

This PR exposes the existing CDK wallet mint_unissued_quotes method through the FFI Wallet.

The core Rust wallet already supports minting paid but unissued mint quotes as part of startup/recovery flows. Exposing this method through cdk-ffi makes the same capability available to generated bindings such as Dart.

Changes

• Add Wallet::mint_unissued_quotes to crates/cdk-ffi
• Convert the core return value into the correct FFI-compatible type
• Generated binding outputs are not committed in this PR because the monorepo does not currently track the generated Dart file.

Testing

• cargo fmt
• cargo test -p cdk-ffi

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.11%. Comparing base (ba17883) to head (c6957ac).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2201      +/-   ##
==========================================
+ Coverage   73.00%   73.11%   +0.11%     
==========================================
  Files         359      359              
  Lines       79608    79639      +31     
==========================================
+ Hits        58114    58232     +118     
+ Misses      21494    21407      -87     

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[j-kon]

@cdk-bot review

[thesimplekid]

This is missing from the trait I guess if it wasn't forced to be exported on the FFI so should add it there.

[j-kon]

Addressed this by adding mint_unissued_quotes to cdk_common::wallet::Wallet, then forwarding it in both the core Wallet trait implementation and the FFI Wallet trait implementation. I also added a small FFI test that calls both the concrete wallet method and the trait method against an empty in-memory store.