Remove client-side authToken cookie handling and rely on secure server cookie

[KGFCH2]

Summary

Eliminate insecure client-side auth token storage during login and use secure cookie-based auth instead.

Details

• Removes client-side authToken cookie writes
• Uses server-managed authentication cookies
• Improves security posture

Acceptance Criteria

• No auth token is stored in browser cookies from client code
• Login still succeeds via secure cookie
• Auth flow remains functional