[SDK] Set up integration tests for `DistributorClient` using local Soroban

[Utilitycoder]

Implement tests that interact with a local Soroban node to verify DistributorClient functionality against a live contract. These tests should be excluded from the standard test run and triggered via a separate command.

[mandyslovestories-sudo]

@mandyslovestories-sudo has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I'd love to work on this issue

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[drips-wave]

Congratulations, @mandyslovestories-sudo! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @mandyslovestories-sudo: 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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