OTA Update Pipeline

Create a shell-based Over-The-Air (OTA) firmware update pipeline for embedded devices. The pipeline should download a firmware image from a remote server, verify checksum, stage it in a temporary directory, and trigger the flashing tool. Logging and rollback must be included.

Constraints

• Accept URL as input.
• Use curl or wget to download.
• Compute SHA256 checksum.
• Compare checksum with .sha256 file.
• On success: call flash.sh <image>.
• On failure: rollback and log error.
• Exit code 0 on success, non-zero on failure.