Add wasm-pack dependency vulnerability monitoring

[collinsadi]

Rust WASM build chain deps are not monitored separately from contracts workspace.

Include scanner crate in cargo audit CI and track wasm-bindgen advisories.

Acceptance criteria:

• Scanner audited on every PR.
• Advisories triaged within SLA.
• Documented in supply-chain policy.

[Kureszn]

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

I've reviewed the issue and believe I can contribute effectively. My experience spans software development, blockchain technologies, cybersecurity and open source collaboration. I take a structured approach to contributions carefully understanding the existing codebase, identifying the root cause and delivering a thoroughly tested implementation.

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