[SDK] Add batchMint() Wrapper

[p3ris0n]

Reward: 200 Points (Stellar Wave 5)

Description
Support the batch minting contract feature in the SDK.

Acceptance Criteria
Add batchMint(recipients: Array<{to: string, amount: bigint}>) method.

[artylobos]

Submitted PR #104 for this issue:
#104

Scope: SDK batchMint(recipients: Array<{ to: string, amount: bigint }>) wrapper, exported recipient type, README usage, and client/mock tests.

Validation:

• cd sdk && npm run build
• cd sdk && npm test -- --runInBand

[victor-olamide]

@victor-olamide has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer, I can work on this issue.

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

[drips-wave]

Congratulations, @victor-olamide! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @victor-olamide: 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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[drips-wave]

This issue has been completed by @victor-olamide as part of the Stellar Wave Program's 5th Wave 🥳

😎 @victor-olamide: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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