Add SDK governance `vetoProposal` and `disableVetoPower` methods

[Levi-Ojukwu]

Description:

The governance contract has admin veto functionality. The SDK needs methods for:

1. vetoProposal(proposalId, reasonHash) — admin blocks a proposal
2. disableVetoPower() — permanently disables admin veto (one-way switch)

Why it matters: Veto power is a critical safety mechanism that needs SDK support.

Acceptance Criteria:

• Create both methods with proper authentication
• Handle VetoPowerDisabled and NotVetoable errors
• Add tests

Relevant Files: contracts/iln_governance/src/lib.rs:736-821, sdk/src/methods/governance.ts

---

[oscar24357]

@oscar24357 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

good morning maintainer, please i would like to work on this issue, can you assign me to it.

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[Hafgans-oss]

@Hafgans-oss has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi! I'd love to work on this issue. I've reviewed the description and acceptance criteria, and I'm confident I can deliver a high-quality solution. I'll ensure all acceptance criteria are fully met, thoroughly test the implementation, and submit a clean, well-documented PR. I'd appreciate it if you could assign this issue to me. Thank you!

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[abayomicornelius]

@abayomicornelius has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Please let me work on this

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[drips-wave]

This issue has been completed by @abayomicornelius as part of the Stellar Wave Program's 7th Wave 🥳

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