Add CI workflow for contract regression tests

[Kings9595]

Add a GitHub Actions workflow that runs the contract test suite and validates ledger snapshots on each push and PR.

[heymide]

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

I've reviewed the task and have a clear implementation plan. Looking forward to contributing with a quality PR.

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

[shelterfaithapps]

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

"Hi maintainers, I would like to work on this issue. Please assign it to me if it's still available."

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

[githoboman]

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

pls let me work on this

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[Osifowora]

@Osifowora 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 can get started on it right away.

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

[drips-wave]

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

🧑‍💻 @shelterfaithapps: 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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