Add unit tests for key transfer sender balance decremented correctly

[Chucks1093]

Summary

The peer-to-peer transfer function must decrement the sender's key balance by exactly the transferred amount. This needs explicit unit test coverage.

Scope

• Register a creator, give a test wallet a balance via buy
• Call transfer_keys and assert the sender balance is reduced by the exact transfer amount
• Assert the recipient balance is increased by the same amount

Acceptance Criteria

• Sender balance decremented by transfer amount
• Recipient balance incremented by transfer amount
• Total supply unchanged after transfer

ETA: 12 hours

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Coordinate on Telegram

[N-thnI]

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

Dear maintainer
Please assign me this issue

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

[yunus-dev-codecrafter]

Hi! I've carefully reviewed the entire task description and fully understand the requirements and expected outcome.
I have experience working on similar tasks and I'm confident I can complete this within about an hour. I'd be happy to take ownership of this issue and submit a clean, well-tested solution promptly.
If it's available, please assign it to me. Thank you!

[Topmatrixmor2014]

@Topmatrixmor2014 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 have studied the details of the issue description and I understood the requirements. I shall deliver with qualitative feedback and promptly.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Topmatrixmor2014 to this issue.

[Ajibose]

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

i will like to work on this

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

[drips-wave]

Congratulations, @Topmatrixmor2014! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Topmatrixmor2014: 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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