Fix syntax error in playground.py

Refactor: use Composio Core SDK as backend engine

Implement real OAuth flow with token exchange + vault credential injection in tool executor

Complete frontend rebuild: 11 pages, professional composio-level design, connections/playground pages, fixed tailwind config

Add dynamic auth configs, connect page, Next.js frontend

fix: use backend. prefix for all internal imports

fix: rename metadata column (reserved in SQLAlchemy)

feat: full platform with dynamic Composio sync, local DB cache, React UI