fix: correct default API key in test environment setup

- Updated default N8N_API_KEY to match test expectations
- Ensured test environment variables are properly set with defaults
- Fixed environment configuration test to work in CI

This resolves the final test failure in CI.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tests/setup/test-env.ts

@@ -46,7 +46,7 @@ function setTestDefaults(): void {
     
     // API
     N8N_API_URL: 'http://localhost:3001/mock-api',
-    N8N_API_KEY: 'test-api-key',
+    N8N_API_KEY: 'test-api-key-12345',
     
     // Server
     PORT: '3001',