Migrate database from MySQL to Supabase PostgreSQL

- Added @supabase/supabase-js client library
- Rewrote database.js to use Supabase API
- Updated server.js health check for Supabase
- Updated db.config.example.js with Supabase format
- Created comprehensive SUPABASE_SETUP.md guide
- Added SQL schema files for easy deployment
- Updated README_DB_CONFIG.md for Supabase

Benefits:
- Managed PostgreSQL database
- Built-in Row Level Security
- Real-time capabilities
- Easy monitoring via dashboard
- Free tier for development

package.json

@@ -20,6 +20,7 @@
     "express": "^4.18.2",
     "socket.io": "^4.6.1",
     "mysql2": "^3.6.5",
+    "@supabase/supabase-js": "^2.39.0",
     "bad-words": "^3.0.4",
     "cors": "^2.8.5"
   },