fix: address security issues and improve Docker implementation

Security Fixes:
- Add command injection prevention in n8n-mcp wrapper with whitelist validation
- Fix race condition in database initialization with proper lock directory creation
- Add flock availability check with fallback behavior
- Implement comprehensive input sanitization in parse-config.js

Improvements:
- Add debug logging support to parse-config.js (DEBUG_CONFIG=true)
- Improve test cleanup error handling with proper error tracking
- Increase integration test timeouts for CI compatibility
- Update test assertions to check environment variables instead of processes

All critical security vulnerabilities identified by code review have been addressed.

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

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

tests/integration/docker/docker-config.test.ts

@@ -56,7 +56,7 @@ describeDocker('Docker Config File Integration', () => {
       cwd: projectRoot,
       stdio: 'inherit'
     });
-  });
+  }, 60000); // Increase timeout to 60s for Docker build
 
   beforeEach(() => {
     tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'docker-config-test-'));