refactor: centralize base64 encoding

services/auth/token.service.ts

@@ -9,6 +9,7 @@ import { EmailVerificationToken } from './auth.types';
 import type { CouchDBDocument } from '../../types';
 import { getDatabaseConfig } from '../../config/unified.config';
 import { logger } from '../logging';
+import { encodeBase64 } from '../../utils/base64';
 
 export interface PasswordResetToken {
   userId: string;
@@ -42,14 +43,8 @@ function fromISO(date: string | Date): Date {
   return date instanceof Date ? date : new Date(date);
 }
 
-function base64Auth(user: string, pass: string): string {
-  // btoa may not exist in some environments (e.g., Node). Fallback to Buffer.
-  if (typeof btoa !== 'undefined') {
-    return btoa(`${user}:${pass}`);
-  }
-
-  return Buffer.from(`${user}:${pass}`).toString('base64');
-}
+const base64Auth = (user: string, pass: string): string =>
+  encodeBase64(`${user}:${pass}`);
 
 export class TokenService {
   private couchBaseUrl: string | null = null;