Adds performance monitoring middleware and admin endpoints for health checks. Replit-Commit-Author: Agent Replit-Commit-Session-Id: c5f0c281-8dd8-4846-b452-4a07bcd21062 Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/9777c70b-fc38-4831-8d6b-78dfffe041b0/5b8fba2e-7c70-4729-817d-64d4f830b47a.jpg