Add default roleId 4 to new users

prisma/migrations/20260910155807_default_user_role/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "user" ALTER COLUMN "roleId" SET DEFAULT 4;

prisma/schema.prisma

@@ -21,7 +21,7 @@ model User {
   image             String?
   createdAt         DateTime            @default(now())
   updatedAt         DateTime            @updatedAt
-  roleId            Int?
+  roleId            Int?                @default(4) // New users default to "User"
   role              UserRole?           @relation(fields: [roleId], references: [id])
   sessions          Session[]
   accounts          Account[]