Add user auth, cart, checkout and personal account for guests and registered users

internal/database/migrate.go

@@ -33,6 +33,50 @@ func Migrate(ctx context.Context, pool *pgxpool.Pool) error {
 			visit_date   DATE NOT NULL DEFAULT CURRENT_DATE
 		)`,
 		`INSERT INTO site_stats (id) VALUES (1) ON CONFLICT (id) DO NOTHING`,
+		`CREATE TABLE IF NOT EXISTS users (
+			id SERIAL PRIMARY KEY,
+			email VARCHAR(255) UNIQUE NOT NULL,
+			password_hash VARCHAR(255) NOT NULL,
+			name VARCHAR(255) NOT NULL DEFAULT '',
+			phone VARCHAR(50) NOT NULL DEFAULT '',
+			address TEXT NOT NULL DEFAULT '',
+			created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+		)`,
+		`CREATE TABLE IF NOT EXISTS carts (
+			id SERIAL PRIMARY KEY,
+			user_id INT REFERENCES users(id) ON DELETE CASCADE,
+			session_key VARCHAR(64) NOT NULL DEFAULT '',
+			updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+		)`,
+		`CREATE UNIQUE INDEX IF NOT EXISTS idx_carts_user ON carts (user_id) WHERE user_id IS NOT NULL`,
+		`CREATE UNIQUE INDEX IF NOT EXISTS idx_carts_session ON carts (session_key) WHERE user_id IS NULL`,
+		`CREATE TABLE IF NOT EXISTS cart_items (
+			id SERIAL PRIMARY KEY,
+			cart_id INT NOT NULL REFERENCES carts(id) ON DELETE CASCADE,
+			product_id INT NOT NULL REFERENCES products(id) ON DELETE CASCADE,
+			quantity INT NOT NULL DEFAULT 1 CHECK (quantity > 0),
+			UNIQUE (cart_id, product_id)
+		)`,
+		`CREATE TABLE IF NOT EXISTS orders (
+			id SERIAL PRIMARY KEY,
+			user_id INT REFERENCES users(id) ON DELETE SET NULL,
+			guest_name VARCHAR(255) NOT NULL DEFAULT '',
+			guest_email VARCHAR(255) NOT NULL DEFAULT '',
+			guest_phone VARCHAR(50) NOT NULL DEFAULT '',
+			address TEXT NOT NULL DEFAULT '',
+			total NUMERIC(10,2) NOT NULL DEFAULT 0,
+			status VARCHAR(50) NOT NULL DEFAULT 'new',
+			created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+		)`,
+		`CREATE TABLE IF NOT EXISTS order_items (
+			id SERIAL PRIMARY KEY,
+			order_id INT NOT NULL REFERENCES orders(id) ON DELETE CASCADE,
+			product_id INT NOT NULL,
+			product_name VARCHAR(255) NOT NULL,
+			price NUMERIC(10,2) NOT NULL,
+			quantity INT NOT NULL CHECK (quantity > 0)
+		)`,
+		`CREATE INDEX IF NOT EXISTS idx_orders_user ON orders (user_id)`,
 	}
 
 	for _, q := range queries {