Remove cache of beacon data files

[naddison36]

Summary

• Store downloaded beacon state SSZ files in temporary storage instead of the project cache directory.
• Create the temporary directory on demand before writing beacon state data.
• Delete all downloaded beacon state files after verifyBalances and verifyDeposits complete.
• Run cleanup in a finally block so files are removed even when verification fails.

Background

Talos containers no longer create /app/cache during their build. Beacon verification actions consequently failed with ENOENT when attempting to write ./cache/state_<slot>.ssz.

Beacon state files are large and only needed while an action is running, so they do not need to persist between actions or container deployments.

Testing

• Ran JavaScript and TypeScript Prettier.
• Verified utils/beacon.js loads successfully.
• Ran git diff --check.

[sparrowDom]

thanks looks more resiliant