refactor: integrate Better-Auth for authentication and remove Supabase dependencies

apps/backend/src/modules/onboarding/services/onboarding.service.ts

@@ -1,4 +1,5 @@
 import { createHash, randomInt } from 'node:crypto';
+import { auth } from '@/lib/auth';
 import { sendMail } from '@/lib/mailer';
 import { db } from '@/lib/prisma';
 import { getSupabaseAdminClient } from '@/lib/supabase-admin';
@@ -10,7 +11,6 @@ import type {
 } from '@repo/api-contract';
 import type { User as SupabaseAuthUser } from '@supabase/supabase-js';
 import { v7 as uuidv7 } from 'uuid';
-import { auth } from '@/lib/auth';
 
 const OTP_LENGTH = 6;
 const OTP_TTL_MINUTES = Number(Bun.env.ONBOARDING_OTP_TTL_MINUTES ?? 10);
@@ -441,7 +441,6 @@ export async function completeOnboarding(input: OnboardingCompleteInput) {
   const complexSlug = await buildUniqueComplexSlug(input.complexName);
 
   const result = await db.$transaction(async (tx) => {
-
     const complex = await tx.complex.create({
       data: {
         id: uuidv7(),