feat(story-1.2): add database migration system with golang-migrate

migrations/001_create_users.up.sql

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+-- Migration: 001_create_users
+-- Description: Create the users table for authentication
+
+CREATE TABLE IF NOT EXISTS users (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    email VARCHAR(255) NOT NULL UNIQUE,
+    password_hash VARCHAR(255) NOT NULL,
+    is_admin BOOLEAN NOT NULL DEFAULT FALSE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Index for email lookup (login)
+CREATE INDEX IF NOT EXISTS idx_users_email ON users(email);
+
+-- Trigger to auto-update updated_at
+CREATE OR REPLACE FUNCTION update_updated_at_column()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = NOW();
+    RETURN NEW;
+END;
+$$ language 'plpgsql';
+
+CREATE TRIGGER update_users_updated_at
+    BEFORE UPDATE ON users
+    FOR EACH ROW
+    EXECUTE FUNCTION update_updated_at_column();