fix: use curl_cffi Chrome TLS impersonation to bypass Cloudflare

chatgpt.com uses Cloudflare's TLS fingerprinting (JA3/JA4) which
blocks Python requests regardless of cookies. curl_cffi impersonates
Chrome's exact TLS handshake, making requests indistinguishable from
a real browser at the transport layer.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements.txt

@@ -1,14 +1,17 @@
 # Editable Git install with no remote (ai-chat-exporter==0.1.0)
 -e /home/jesse/services/ai-chatexport
 certifi==2026.2.25
+cffi==2.0.0
 charset-normalizer==3.4.4
 click==8.1.7
+curl_cffi==0.14.0
 idna==3.11
 iniconfig==2.3.0
 markdown-it-py==4.0.0
 mdurl==0.1.2
 packaging==26.0
 pluggy==1.6.0
+pycparser==3.0
 Pygments==2.19.2
 PyJWT==2.8.0
 pytest==8.1.1