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

supabase-functions.sql

@@ -0,0 +1,50 @@
+-- Supabase SQL Helper Functions for Connect-5
+-- Run this in your Supabase SQL Editor after creating the tables
+
+-- Function to increment wins
+CREATE OR REPLACE FUNCTION increment_wins(player_id BIGINT)
+RETURNS void AS $$
+BEGIN
+    UPDATE players 
+    SET total_wins = total_wins + 1 
+    WHERE id = player_id;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Function to increment losses
+CREATE OR REPLACE FUNCTION increment_losses(player_id BIGINT)
+RETURNS void AS $$
+BEGIN
+    UPDATE players 
+    SET total_losses = total_losses + 1 
+    WHERE id = player_id;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Function to increment draws
+CREATE OR REPLACE FUNCTION increment_draws(player_id BIGINT)
+RETURNS void AS $$
+BEGIN
+    UPDATE players 
+    SET total_draws = total_draws + 1 
+    WHERE id = player_id;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Optional: Function to get player stats
+CREATE OR REPLACE FUNCTION get_player_stats(player_username VARCHAR)
+RETURNS TABLE (
+    id BIGINT,
+    username VARCHAR,
+    total_wins INT,
+    total_losses INT,
+    total_draws INT,
+    created_at TIMESTAMP WITH TIME ZONE
+) AS $$
+BEGIN
+    RETURN QUERY
+    SELECT p.id, p.username, p.total_wins, p.total_losses, p.total_draws, p.created_at
+    FROM players p
+    WHERE p.username = player_username;
+END;
+$$ LANGUAGE plpgsql;