Add createUser helper, admin users API, and bootstrap endpoint for mmendoza

src/lib/auth.ts

@@ -14,6 +14,15 @@ export async function verifyPassword(password: string, hash: string) {
   return bcrypt.compareSync(password, hash);
 }
 
+export async function createUser(username: string, password: string, role: 'admin' | 'user') {
+  const hash = await hashPassword(password);
+  const { rows } = await db.query(
+    'INSERT INTO users (username, password_hash, role) VALUES ($1, $2, $3) ON CONFLICT (username) DO UPDATE SET password_hash = EXCLUDED.password_hash, role = EXCLUDED.role RETURNING id, username, role',
+    [username, hash, role]
+  );
+  return rows[0];
+}
+
 export async function authenticateUser(username: string, password: string) {
   const { rows } = await db.query('SELECT id, username, password_hash, role FROM users WHERE username = $1', [username]);
   if (rows.length === 0) return null;