feat: add disputeRelease and resolveDispute methods

[MarcusDavidG]

Summary

The contract exposes dispute_release and resolve_dispute but the SDK has no methods for them.

Methods to add

async disputeRelease(caller: string, invoiceId: number): Promise<{ txHash: string }>
async resolveDispute(caller: string, invoiceId: number, release: boolean): Promise<{ txHash: string }>

Acceptance criteria

• Both methods added to SharpyClient
• JSDoc with param descriptions
• Exported types updated if needed