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;

services/database/ProductionDatabaseStrategy.ts

@@ -12,6 +12,7 @@ import { AccountStatus } from '../auth/auth.constants';
 import { DatabaseStrategy, DatabaseError } from './types';
 import { getDatabaseConfig } from '../../config/unified.config';
 import { logger } from '../logging';
+import { encodeBase64 } from '../../utils/base64';
 
 export class ProductionDatabaseStrategy implements DatabaseStrategy {
   private baseUrl: string;
@@ -22,7 +23,7 @@ export class ProductionDatabaseStrategy implements DatabaseStrategy {
     const dbConfig = getDatabaseConfig();
 
     this.baseUrl = dbConfig.url;
-    this.auth = btoa(`${dbConfig.username}:${dbConfig.password}`);
+    this.auth = encodeBase64(`${dbConfig.username}:${dbConfig.password}`);
 
     logger.db.query('Initializing production database strategy', {
       url: dbConfig.url,

services/mailgun.service.ts

@@ -7,6 +7,7 @@ import { getMailgunConfig, type MailgunConfig } from './mailgun.config';
 import { getAppConfig } from '../config/unified.config';
 import { logger } from './logging';
 import { normalizeError } from '../utils/error';
+import { encodeBase64 } from '../utils/base64';
 
 interface EmailTemplate {
   subject: string;
@@ -146,7 +147,7 @@ export class MailgunService {
         {
           method: 'POST',
           headers: {
-            Authorization: `Basic ${btoa(`api:${this.config.apiKey}`)}`,
+            Authorization: `Basic ${encodeBase64(`api:${this.config.apiKey}`)}`,
           },
           body: formData,
         }

utils/base64.ts

@@ -0,0 +1,7 @@
+export const encodeBase64 = (value: string): string => {
+  if (typeof btoa !== 'undefined') {
+    return btoa(value);
+  }
+
+  return Buffer.from(value, 'utf-8').toString('base64');
+};