Build invoice rollover helper

[Kingsman-99]

Labels: complexity: high

Expose the contract's rollover_invoice function through a typed SDK method. When an invoice expires without full funding, callers should be able to roll it over into a new invoice preserving all settings.

Acceptance criteria:

• rolloverInvoice(invoiceId, newDeadline, caller) builds and submits the rollover transaction
• Returns the new invoice ID from the contract return value
• Validates newDeadline > Date.now() / 1000 before submission
• Preserves all original invoice options automatically

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[Osifowora]

@Osifowora has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

​Hi maintainer, I would love to work on this issue. I can get started on it right away.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Osifowora to this issue.

[drips-wave]

Congratulations, @Osifowora! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Osifowora: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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