fix existing user enrollment for instructors

src/auth/routes.ts

@@ -826,10 +826,9 @@ authRoutes.post('/instructor/students', authRequired, async (c) => {
 
   const email = body.data.email.toLowerCase()
   const existingUser = await findUserByEmail(email)
-  if (existingUser) return c.json({ error: 'email_already_registered' }, 409)
 
   try {
-    const user = await createManagedUser({
+    const user = existingUser ?? await createManagedUser({
       email,
       password: body.data.password,
       name: body.data.name,
@@ -839,17 +838,25 @@ authRoutes.post('/instructor/students', authRequired, async (c) => {
       licenseCode: body.data.licenseCode,
     })
 
-    await prisma.userAppRole.create({
-      data: {
+    await prisma.userAppRole.upsert({
+      where: {
+        userId_appKey_roleCode: {
+          userId: user.id,
+          appKey: 'LMS',
+          roleCode: 'STUDENT',
+        },
+      },
+      create: {
         userId: user.id,
         appKey: 'LMS',
         roleCode: 'STUDENT',
         assignedById: instructor.id,
       },
+      update: {},
     })
 
-    const createdUser = await findUserById(user.id)
-    return c.json({ user: userResponse(createdUser ?? user) }, 201)
+    const resolvedUser = await findUserById(user.id)
+    return c.json({ user: userResponse(resolvedUser ?? user) }, existingUser ? 200 : 201)
   } catch {
     return c.json({ error: 'user_create_failed' }, 400)
   }