test: update mocks to use unified config structure

- Update mailgun service test mock to use unifiedConfig.app.baseUrl
- Update database service test mock to use unifiedConfig.app.baseUrl
- Ensures test mocks reflect actual unified configuration structure
- Maintains test compatibility after config system consolidation

services/__tests__/mailgun.service.test.ts

@@ -12,9 +12,11 @@ jest.mock('../mailgun.config', () => ({
 }));
 
 // Mock the app config
-jest.mock('../../config/app.config', () => ({
-  appConfig: {
-    baseUrl: 'http://localhost:3000',
+jest.mock('../../config/unified.config', () => ({
+  unifiedConfig: {
+    app: {
+      baseUrl: 'http://localhost:3000',
+    },
   },
 }));