Production-grade hardening: 8 tasks, Efficiency Metrics, ERD Viz, UI Overhaul

fixed metrics

feat: implement dynamic ERD visualization, premium dashboard UI, and professional global README

fixed errors v2

feat: expand to 7 tasks (2E/3M/2H) + engine hardening

Fix: max_steps consistency + all pre-submit fixes

Initial Submission: SQL Schema Migration Agent for OpenEnv Hackathon