Implements HTTP middleware that enforces session authentication by validating
session cookies and making claims available via ClaimsFromContext. Rejects
requests without valid session cookies with 401 Unauthorized.
Tested via four test cases:
- Missing session cookie rejection
- Valid cookie acceptance with claims extraction
- Expired cookie rejection
- Tampered cookie rejection
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
