Add IPFS invoice metadata pinning with CID verification

[Kingsman-99]

Overview

Allow invoice creators to attach structured metadata stored on IPFS. The CID is stored in the contract memo field. The SDK should pin metadata to IPFS, verify the CID matches the content, and enrich invoice reads with the resolved metadata.

Requirements

• pinInvoiceMetadata(metadata: InvoiceMetadata): Promise — pins JSON to IPFS, returns CID
• InvoiceMetadata { title, description, lineItems: LineItem[], attachmentCIDs: string[] }
• verifyCID(cid, content): Promise — fetches and checks content hash
• enrichInvoice(invoiceId): Promise — merges on-chain + IPFS data
• Support IPFS HTTP gateway and kubo RPC backends (configurable)
• Tests with mock IPFS server; CID mismatch handled gracefully

Acceptance Criteria

• Metadata pinned and CID returned
• CID verification detects tampering
• enrichInvoice merges data correctly
• Both gateway and kubo backends work
• npm test passes with zero failures
• TypeScript compiles with zero errors
• ESLint passes with zero errors

Definition of Done

All CI checks must pass before the PR is reviewed.

[Alimzy]

@Alimzy has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Hi! I'd like to work on this issue.

I'm a software engineer with hands-on experience in testing, debugging, and building reliable features across the stack. I'm confident I can take this on and deliver a solid, well-tested solution that follows the project's existing conventions.

I'll make sure to cover the core functionality as well as relevant edge cases to keep things reliable and regression-resistant.

Let me know if I can get started, and I'll provide updates as I progress.

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[Cherry-Olaa]

@Cherry-Olaa has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

Please Can I be assign this task I will love to work on it
I understand what’s stated and how to resolve it

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[maztah1]

@maztah1 has applied to work on this issue as part of the Stellar Wave Program's 9th wave.

can i work on this issue please

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Congratulations, @maztah1! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on September 30, 2026.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@maztah1's PR #948 was approved and merged by @Kingsman-99.

🏆 @maztah1: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (920 total points). Track your full progress on GrantFox.

👏 Great work, @maztah1! Keep contributing to Stellar-split.

[drips-wave]

This issue has been completed by @maztah1 as part of the Stellar Wave Program's 9th Wave 🥳

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