WKS-2687 - Add PlatformCrypto to PlatformContext

[ehl-jf]

Summary

• Adds a PlatformCrypto interface (hash, hmac, randomBytes) to the worker-facing PlatformContext type.
• Signatures match the runtime implementation already merged in platform-extension (worker sandbox's context.crypto).

Related tickets

• WKS-2688 (crypto.hash)
• WKS-2687 (crypto.hmac)
• WKS-2689 (crypto.randomBytes)

Test plan

• npm run build (tsc) compiles cleanly
• dist/index.d.ts contains the PlatformCrypto interface and crypto: PlatformCrypto member
• After merge, confirm CI auto-publishes the new minor version, then bump the jfrog-workers pin in platform-extension's service/package.json and frontend/package.json and regenerate Monaco typings