chore(deps): bump curl_cffi to 0.16.0 in constraints.txt (LeyckerS#141)

Supersedes LeyckerS#139, which conflicted after LeyckerS#137 and LeyckerS#138 landed in the same file.
Same one-line change, already green on Dependabot's branch.

Stays inside the >=0.7,<1 ceiling restored in LeyckerS#136; the dependency-contract job
verifies the bound and both pip check installs.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: LeyckerS

constraints.txt

@@ -3,7 +3,7 @@
 
 aiohttp==3.14.2
 playwright==1.62.0
-curl_cffi==0.15.0
+curl_cffi==0.16.0
 certifi==2026.7.22
 cffi==2.1.0
 greenlet==3.5.4