Add fuzz tests for `cancel_invoice`

[Levi-Ojukwu]

Difficulty: Medium

Description:

Acceptance Criteria:

• Property test that cancel_invoice never panics
• Test with random invoice IDs and states

Relevant Files: contracts/fuzz/src/lib.rs

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[ekwe7]

I will love to work on this project

[vickachi]

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

I'm a full-stack Software Engineer
I'd love to take this on — thanks for considering me

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[stephanieoghenemega-eng]

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

hello maintainer, kindly assign these issues to me. Thank you

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

[drips-wave]

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

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[drips-wave]

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

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