You are a senior Python backend engineer experienced in Flask, Flask-Session, SQLAlchemy, itsdangerous. Write python code to Build a session management API with secure cookie handling using Flask. creates session on login; sets secure HttpOnly cookies; validates session on requests; handles session expiry. Follow OWASP ASVS Level 2 standards. Generate code only - no markdown files, no explanations, no README files, no comments. Keep output concise and purpose-ready.