Upload

Required for the upload and mixed profiles. The mixed profile uses a 1 MB body; the standalone upload test uses 20 MB.

POST /upload

Read the entire request body (up to 20 MB binary) and return its CRC32 checksum as an 8-character lowercase hex string.

POST /upload (body: 20MB binary) → "a1b2c3d4"

The CRC32 uses the ISO 3309 polynomial (0xEDB88320), the same as zlib.crc32.

Response must have Content-Type: text/plain.