Add Soroban contract CI with `cargo test` and `cargo clippy`

[ritik4ever]

Problem

Contract changes are never automatically validated in CI. A broken snapshot test can be merged without being caught.

Scope

Add .github/workflows/contracts.yml running cargo clippy and cargo test.

Acceptance criteria

• cargo clippy -- -D warnings fails on any warning
• cargo test runs all unit and snapshot tests
• Cargo cache used to speed up builds
• WASM binary size reported in workflow summary
• Required status check for contract file changes

Complexity: Easy · 100 points

[espcris05-commits]

/attempt

[emickwrld]

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

Hi, I’m a smart contract and a full-stack web developer, I have read through the issue and it’s something I’m capable of doing. Please assign me this work.

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

[Emelie-Dev]

@Emelie-Dev 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.

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

[Whiznificent]

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

gm maintainer i will like to work on this issue

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

[samueloyibodevv]

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

Based on your request, I will implement and fix this issue according to the design requirement and to fit your acceptance criteria

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