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-schema-complete.sql

@@ -0,0 +1,114 @@
+-- Complete Supabase Schema for Connect-5
+-- Copy and paste this entire file into Supabase SQL Editor and run it
+
+-- Create players table
+CREATE TABLE IF NOT EXISTS players (
+    id BIGSERIAL PRIMARY KEY,
+    username VARCHAR(50) UNIQUE NOT NULL,
+    total_wins INT DEFAULT 0,
+    total_losses INT DEFAULT 0,
+    total_draws INT DEFAULT 0,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_username ON players(username);
+
+-- Create active sessions table
+CREATE TABLE IF NOT EXISTS active_sessions (
+    session_id VARCHAR(100) PRIMARY KEY,
+    player_id BIGINT NOT NULL,
+    username VARCHAR(50) NOT NULL,
+    connected_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    last_heartbeat TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    FOREIGN KEY (player_id) REFERENCES players(id) ON DELETE CASCADE
+);
+
+-- Create game state enum type
+DO $$ BEGIN
+    CREATE TYPE game_state_enum AS ENUM ('pending', 'active', 'completed', 'abandoned');
+EXCEPTION
+    WHEN duplicate_object THEN null;
+END $$;
+
+-- Create games table
+CREATE TABLE IF NOT EXISTS games (
+    id BIGSERIAL PRIMARY KEY,
+    player1_id BIGINT NOT NULL,
+    player2_id BIGINT NOT NULL,
+    player1_username VARCHAR(50) NOT NULL,
+    player2_username VARCHAR(50) NOT NULL,
+    board_size INT DEFAULT 15,
+    winner_id BIGINT,
+    game_state game_state_enum DEFAULT 'pending',
+    started_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    completed_at TIMESTAMP WITH TIME ZONE,
+    FOREIGN KEY (player1_id) REFERENCES players(id),
+    FOREIGN KEY (player2_id) REFERENCES players(id),
+    FOREIGN KEY (winner_id) REFERENCES players(id)
+);
+
+-- Create game moves table
+CREATE TABLE IF NOT EXISTS game_moves (
+    id BIGSERIAL PRIMARY KEY,
+    game_id BIGINT NOT NULL,
+    player_id BIGINT NOT NULL,
+    row_position INT NOT NULL,
+    col_position INT NOT NULL,
+    move_number INT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    FOREIGN KEY (game_id) REFERENCES games(id) ON DELETE CASCADE,
+    FOREIGN KEY (player_id) REFERENCES players(id)
+);
+CREATE INDEX IF NOT EXISTS idx_game ON game_moves(game_id);
+
+-- Enable Row Level Security (RLS)
+ALTER TABLE players ENABLE ROW LEVEL SECURITY;
+ALTER TABLE active_sessions ENABLE ROW LEVEL SECURITY;
+ALTER TABLE games ENABLE ROW LEVEL SECURITY;
+ALTER TABLE game_moves ENABLE ROW LEVEL SECURITY;
+
+-- Create policies to allow all operations (adjust based on your security needs)
+DROP POLICY IF EXISTS "Allow all operations on players" ON players;
+CREATE POLICY "Allow all operations on players" ON players FOR ALL USING (true);
+
+DROP POLICY IF EXISTS "Allow all operations on active_sessions" ON active_sessions;
+CREATE POLICY "Allow all operations on active_sessions" ON active_sessions FOR ALL USING (true);
+
+DROP POLICY IF EXISTS "Allow all operations on games" ON games;
+CREATE POLICY "Allow all operations on games" ON games FOR ALL USING (true);
+
+DROP POLICY IF EXISTS "Allow all operations on game_moves" ON game_moves;
+CREATE POLICY "Allow all operations on game_moves" ON game_moves FOR ALL USING (true);
+
+-- Helper Functions
+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;
+
+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;
+
+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;
+
+-- Success message
+DO $$
+BEGIN
+    RAISE NOTICE '✅ Connect-5 database schema created successfully!';
+END $$;