zip protection to zip converter

[blackheart-5]

Problem

ZipConverter had no protection against zip bombs. A maliciously crafted
zip could cause OOM or infinite recursion if these exist:

• High compression ratio (small zip → massive uncompressed size)
• Millions of tiny files
• Deeply nested zips (zip inside zip inside zip...)

Changes

• Added ZIP_UNCOMPRESSED_SIZE_THRESHOLD = 100 MB — rejects zips whose
  total uncompressed size exceeds limit
• Added MAX_FILE_COUNT = 1000 — rejects zips with too many files
• Added MAX_DEPTH = 3 — rejects zips nested deeper than 3 levels
• Depth counter passed through convert_stream recursively

Testing

Manually verified with normal zips and simulated oversized inputs.

[blackheart-5]

@microsoft-github-policy-service agree