Add PocketFox HTTP URL parser tests

[pagefarms]

Summary

• add a small offline C test binary for the public pf_parse_url helper
• cover HTTPS defaults, HTTP custom ports, bare-host defaults, query-only paths, and invalid empty-host URLs
• provide local SSL stubs so the parser tests compile without mbedTLS or Mac OS X Tiger SDKs

Validation

• cc -std=c99 -Wall -Wextra -I. tests/test_pocketfox_http.c pocketfox_http.c -o /tmp/pocketfox_http_tests && /tmp/pocketfox_http_tests
• cc -std=c99 -Wall -Wextra -fsyntax-only -I. pocketfox_http.c tests/test_pocketfox_http.c
• git diff --check

Bounty: Scottcjn/rustchain-bounties#1589