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>

src/http-server.ts

@@ -14,6 +14,11 @@ import { isN8nApiConfigured } from './config/n8n-api';
 import dotenv from 'dotenv';
 import { readFileSync } from 'fs';
 import { getStartupBaseUrl, formatEndpointUrls, detectBaseUrl } from './utils/url-detector';
+import { 
+  negotiateProtocolVersion, 
+  logProtocolNegotiation,
+  N8N_PROTOCOL_VERSION 
+} from './utils/protocol-version';
 
 dotenv.config();
 
@@ -342,10 +347,20 @@ export async function startFixedHTTPServer() {
           
           switch (jsonRpcRequest.method) {
             case 'initialize':
+              // Negotiate protocol version for this client/request
+              const negotiationResult = negotiateProtocolVersion(
+                jsonRpcRequest.params?.protocolVersion,
+                jsonRpcRequest.params?.clientInfo,
+                req.get('user-agent'),
+                req.headers
+              );
+              
+              logProtocolNegotiation(negotiationResult, logger, 'HTTP_SERVER_INITIALIZE');
+              
               response = {
                 jsonrpc: '2.0',
                 result: {
-                  protocolVersion: '2024-11-05',
+                  protocolVersion: negotiationResult.version,
                   capabilities: {
                     tools: {},
                     resources: {}