This is an automated pull request to release the candidate branch into production, which will trigger a deployment.
It was created by the [Production PR] action.

Summary by cubic

Replaced regex-based base64 validation with a decode-and-reencode check to prevent stack overflows and false positives in file uploads. Ignored the unused GovCloud session token in Security Hub credentials and clarified the .env example; fixes CS-355 (internal server error when uploading PNGs to the Network Diagram document).

• Bug Fixes
  • Validate base64 by decoding and re-encoding; reject mismatches.
  • Throw clear errors: "Invalid file data. Expected base64 string." and "File cannot be empty."

^{Written for commit ff1f86d. Summary will update on new commits.}