Pull `Cargo.lock` (reproducible builds) into released Wasm CI

[kilodesodiq-arch]

Problem Statement. Building the contract in CI does not enforce Cargo.lock
reproducibility, nor does it fail when Cargo.lock is out of date.

Technical Context.
app/onchain/Cargo.toml,
.github/workflows/contract-ci.yml.

Expected Outcome. New CI step cargo check --locked and an explicit assertion that
any PR introducing a Cargo.toml change bumps Cargo.lock.

Acceptance Criteria.

• PR changing only Cargo.toml (no Cargo.lock) fails CI.

Files or modules likely to be affected.
.github/workflows/contract-ci.yml.

Difficulty. Easy
Estimated effort. XS

---

---

Backlog item #99 from `docs/maintainer-issue-backlog.md.

[Oluwasuyi-Oluwatimilehin-Daniel]

I’ve reviewed the details and feel confident that I can investigate and implement a solid solution for this. If this issue is currently unassigned and open for external contributors, could you please assign it to me? I will get started on a fix right away and submit a Pull Request as soon as it's ready. Please let me know if there are any specific guidelines or approaches you'd like me to follow for this particular task. Thanks.

[Ayinkx1]

Hi i would like to work on this issue please assign to me
I can do it perfectly

[grantfox-oss]

🦊 GrantFox — @Ayinkx1 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #307)
2. Your PR will be reviewed by the ChainForgee maintainers

Good luck! Track your progress on GrantFox.