Fix three critical code bugs

[elnormous]

Fix three critical bugs in HTTPRequest.hpp for IPv6 URI parsing, Transfer-Encoding header handling, and chunk size parsing.

• parseUri now correctly handles IPv6 bracketed hosts and optional ports (e.g., [::1]:80).
• Transfer-Encoding header parsing is now case-insensitive and correctly tokenizes comma-separated values, accepting "chunked" and rejecting unsupported encodings.
• Chunk size parsing now correctly ignores chunk extensions after a semicolon, as specified by RFC 7230.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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