Add admin role

Allow privileged users to administer the system.

prisma/schema.prisma

@@ -249,12 +249,20 @@ model Session {
     user         User     @relation(fields: [userId], references: [id], onDelete: Cascade)
 }
 
+enum UserRole {
+    ADMIN
+    USER
+}
+
 model User {
-    id                String             @id @default(uuid()) @db.Uuid
-    name              String?
-    email             String?            @unique
-    emailVerified     DateTime?
-    image             String?
+    id            String    @id @default(uuid()) @db.Uuid
+    name          String?
+    email         String?   @unique
+    emailVerified DateTime?
+    image         String?
+
+    role UserRole @default(USER)
+
     accounts          Account[]
     sessions          Session[]
     organizationUsers OrganizationUser[]