Fix register transaction typing for cross-site password update.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/auth/auth.service.ts

@@ -99,17 +99,19 @@ export class AuthService {
 
     const linkedExistingAccount = Boolean(existingUser);
 
-    const user = await this.prisma.$transaction(async (tx) => {
-      let account = existingUser;
+    const userId = await this.prisma.$transaction(async (tx) => {
+      let userId: bigint;
 
-      if (account) {
+      if (existingUser) {
         // Cross-site join: replace Meshkee password with the one entered on this signup.
-        account = await tx.user.update({
-          where: { id: account.id },
+        const updated = await tx.user.update({
+          where: { id: existingUser.id },
           data: { passwordHash },
+          select: { id: true },
         });
+        userId = updated.id;
       } else {
-        account = await tx.user.create({
+        const created = await tx.user.create({
           data: {
             cellNumber: dto.cellNumber,
             passwordHash,
@@ -118,20 +120,22 @@ export class AuthService {
             lastName: dto.lastName,
             cellVerifiedAt: smsEnabled ? null : new Date(),
           },
+          select: { id: true },
         });
+        userId = created.id;
       }
 
       await tx.businessCustomer.create({
         data: {
           businessId: business.id,
-          userId: account.id,
+          userId,
         },
       });
 
       const hasCustomerRole = await tx.userRole.findUnique({
         where: {
           userId_roleId: {
-            userId: account.id,
+            userId,
             roleId: customerRole.id,
           },
         },
@@ -140,16 +144,16 @@ export class AuthService {
       if (!hasCustomerRole) {
         await tx.userRole.create({
           data: {
-            userId: account.id,
+            userId,
             roleId: customerRole.id,
           },
         });
       }
 
-      return account;
+      return userId;
     });
 
-    const authUser = await this.getAuthUser(user.id);
+    const authUser = await this.getAuthUser(userId);
     const tokens = await this.issueTokens(authUser);
 
     return {