create admin user on first start

backend/migrations/20250829140914_create_admin_user.sql

@@ -0,0 +1,11 @@
+INSERT INTO users (
+	name,
+	email,
+	hash,
+	admin
+) VALUES (
+	'admin',
+	'admin@example.com',
+	'$argon2id$v=19$m=19456,t=2,p=1$H1WsElL4921/WD5oPkY7JQ$aHudNG8z0ns3pRULfuDpuEkxPUbGxq9AHC4QGyt5odc',
+	true
+);