fix(contribution-service): add parent .env path for shared config

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/contribution-service/src/app.module.ts

@@ -16,6 +16,7 @@ import { JwtAuthGuard } from './shared/guards/jwt-auth.guard';
       envFilePath: [
         `.env.${process.env.NODE_ENV || 'development'}`,
         '.env',
+        '../.env', // 父目录共享 .env
       ],
       ignoreEnvFile: false,
     }),