feat: update cdk to 0.15

[thesimplekid]

No description provided.

[a1denvalu3]

CI Failure Analysis

The unit test compilation is failing with:

Unresolved reference 'MultiMintWallet'

Root Cause

This PR updates Numo from CDK 0.14.4-rc.0 → 0.15.0-rc.3. CDK 0.15 has breaking API changes:

Old API (0.14)	New API (0.15)
MultiMintWallet	WalletRepository
mintQuote()	changed
checkMintQuote()	changed
mint()	changed
getBalances()	changed

The test files still reference the old MultiMintWallet class which no longer exists in CDK 0.15:

• AutoWithdrawManagerTest.kt
• LightningMintHandlerTest.kt

Fix Required

Update the test files to use the new CDK 0.15 API - specifically update the imports and method calls to match the new WalletRepository interface.

[thesimplekid]

@a1denvalu3 Thanks fixed the tests I think