Add unit tests for Address parsing with corrupted checksums

[Emrys02]

Preventing malicious or accidental corrupted address strings from being accepted is critical for security and fault tolerance.

Implementation Guidelines

Key Files: crates/core/src/types/ (in the test module).

• Provide dummy valid strkeys, mutate the last few validation characters, and assert that Address::from_string correctly yields an error.

Expectations

What done looks like: Tests explicitly pass only when invalid strkeys are correctly rejected.

For any question, reach me on Discord: emry_ss

[N-thnI]

@N-thnI has applied to work on this issue as part of the Stellar Wave Program's 3rd 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.

[drips-wave]

Congratulations, @N-thnI! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @N-thnI: 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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