Dedupe classification columns in CSV output

Multiple keywords (English and Chinese) in PROXY_CLASSIFICATIONS map to
the same classification value, which caused columns like "proxy", "vpn",
"webhost", etc. to appear twice in the CSV header.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Dedupe classification columns in CSV output

Multiple keywords (English and Chinese) in PROXY_CLASSIFICATIONS map to
the same classification value, which caused columns like "proxy", "vpn",
"webhost", etc. to appear twice in the CSV header.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>