refactor: migrate services from app.config to unified config

- Update email verification template to use unifiedConfig
- Update ProductionDatabaseStrategy to use databaseConfig from unified config
- Update mailgun service to use unifiedConfig for baseUrl
- Provides consistent configuration access across all services
- Part of migration to single source of truth configuration system

services/database/ProductionDatabaseStrategy.ts

@@ -10,7 +10,7 @@ import {
 } from '../../types';
 import { AccountStatus } from '../auth/auth.constants';
 import { DatabaseStrategy, DatabaseError } from './types';
-import { getDatabaseConfig } from '../../config/app.config';
+import { databaseConfig } from '../../config/unified.config';
 import { logger } from '../logging';
 
 export class ProductionDatabaseStrategy implements DatabaseStrategy {
@@ -18,8 +18,8 @@ export class ProductionDatabaseStrategy implements DatabaseStrategy {
   private auth: string;
 
   constructor() {
-    // Get CouchDB configuration from centralized config
-    const dbConfig = getDatabaseConfig();
+    // Get CouchDB configuration from unified config
+    const dbConfig = databaseConfig;
 
     this.baseUrl = dbConfig.url;
     this.auth = btoa(`${dbConfig.username}:${dbConfig.password}`);