feat: implement n8n integration improvements and protocol version negotiation

- Add intelligent protocol version negotiation (2024-11-05 for n8n, 2025-03-26 for standard clients)
- Fix memory leak potential with async cleanup and connection close handling
- Enhance error sanitization for production environments
- Add schema validation for n8n nested output workaround
- Improve Docker security with unpredictable UIDs/GIDs
- Create n8n-friendly tool descriptions to reduce schema validation errors
- Add comprehensive protocol negotiation test suite

Addresses code review feedback:
- Protocol version inconsistency resolved
- Memory management improved
- Error information leakage fixed
- Docker security enhanced

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

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

package.json

@@ -40,6 +40,7 @@
     "fetch:templates:robust": "node dist/scripts/fetch-templates-robust.js",
     "prebuild:fts5": "npx tsx scripts/prebuild-fts5.ts",
     "test:templates": "node dist/scripts/test-templates.js",
+    "test:protocol-negotiation": "npx tsx src/scripts/test-protocol-negotiation.ts",
     "test:workflow-validation": "node dist/scripts/test-workflow-validation.js",
     "test:template-validation": "node dist/scripts/test-template-validation.js",
     "test:essentials": "node dist/scripts/test-essentials.js",