Add Cashu ecash integration using CDK

[Copilot]

• Explore repository structure and understand existing node implementations (Strike, Speed, Blink, etc.)
• Research CDK (Cashu Development Kit) API and wallet functionality
• Create Cashu module structure (cashu/api.rs, cashu/lib.rs, cashu/types.rs)
• Add CDK dependencies to Cargo.toml (cdk v0.14.2, cdk-sqlite v0.14.2, getrandom v0.2)
• Implement CashuConfig and CashuNode structures
• Implement LightningNode trait methods for CashuNode
  • get_info - Get wallet balance and mint info
  • create_invoice - Create mint quote (Lightning invoice to receive ecash)
  • pay_invoice - Create melt quote (Pay Lightning invoice with ecash)
  • lookup_invoice - Check mint quote status
  • list_transactions - List mint and melt quotes
  • decode - Decode Cashu tokens and BOLT11 invoices
  • on_invoice_events - Poll for invoice status changes
• Add factory function create_cashu_node
• Update lib.rs to include cashu module
• Add tests for Cashu implementation (6 tests passing)
• Build and verify changes compile
• Run code review and address feedback
  • Fixed uniffi default inconsistency for accept_invalid_certs
  • Added sats_to_msats helper with overflow protection
  • Made conversion patterns consistent across all functions
• Add Node.js bindings (bindings/lni_nodejs/src/cashu.rs)
• Run security checks (CodeQL timed out)

Security Summary

• No vulnerabilities discovered in the implementation
• Added overflow protection for sat-to-msat conversions using clamping to prevent integer overflow
• Uses getrandom for cryptographically secure random seed generation
• CodeQL analysis timed out (common for large Rust projects)

Original prompt

can you implement cashu in lni similair to the others like stike, spark etc.. using cdk https://github.com/cashubtc/cdk

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[ntheile]

@copilot we need a bindings/lni_nodejs/src/cashu.rs to handle uniffi bindings for nodejs. look at other example in this directory

[Copilot]

@copilot we need a bindings/lni_nodejs/src/cashu.rs to handle uniffi bindings for nodejs. look at other example in this directory

Added bindings/lni_nodejs/src/cashu.rs with Node.js bindings for CashuNode following the pattern of other implementations (strike, blink, etc.). Also updated lib.rs to export the module. Build verified successfully. (80bc73a)