Add regression test for buy event containing correct buyer address

[Chucks1093]

Summary
Buy event fee field tests exist, but the buyer address field in the emitted event is not independently asserted. A regression test that confirms the buyer address in the event matches the caller address prevents a silent field mismatch.

Scope

• add a regression test that performs a buy and inspects the emitted buy event
• assert the buyer address field matches the address that initiated the call
• assert the field is present and non-zero

Acceptance Criteria

• the buyer address in the buy event matches the caller
• the test fails if the field is absent or contains a different address
• the test is distinct from existing buy fee field tests

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[exronnin]

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

Hi, I would love to work on this issue, I have proven experience and track record building user interfaces and experience. I will add regression test for buy event containing correct buyer address and ensure that everything works as expected.

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

[godamongstmen897]

@godamongstmen897 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Can you assign me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @godamongstmen897 to this issue.

[drips-wave]

Congratulations, @godamongstmen897! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @godamongstmen897: 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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