fix: implement Single-Session architecture to resolve MCP stream errors

- Add ConsoleManager to prevent console output interference with StreamableHTTPServerTransport
- Implement SingleSessionHTTPServer with persistent session reuse
- Create N8NMCPEngine for clean service integration
- Add automatic session expiry after 30 minutes of inactivity
- Update logger to be HTTP-aware during active requests
- Maintain backward compatibility with existing deployments

This fixes the "stream is not readable" error by implementing the Hybrid
Single-Session architecture as documented in MCP_ERROR_FIX_PLAN.md

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

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

scripts/test-single-session.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+# Test script for single-session HTTP server
+
+set -e
+
+echo "🧪 Testing Single-Session HTTP Server..."
+echo
+
+# Generate test auth token if not set
+if [ -z "$AUTH_TOKEN" ]; then
+  export AUTH_TOKEN="test-token-$(date +%s)"
+  echo "Generated test AUTH_TOKEN: $AUTH_TOKEN"
+fi
+
+# Start server in background
+echo "Starting server..."
+MCP_MODE=http npm start > server.log 2>&1 &
+SERVER_PID=$!
+
+# Wait for server to start
+echo "Waiting for server to start..."
+sleep 3
+
+# Check health endpoint
+echo
+echo "Testing health endpoint..."
+curl -s http://localhost:3000/health | jq .
+
+# Test authentication failure
+echo
+echo "Testing authentication failure..."
+curl -s -X POST http://localhost:3000/mcp \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer wrong-token" \
+  -d '{"jsonrpc":"2.0","method":"tools/list","id":1}' | jq .
+
+# Test successful request
+echo
+echo "Testing successful request..."
+curl -s -X POST http://localhost:3000/mcp \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer $AUTH_TOKEN" \
+  -d '{"jsonrpc":"2.0","method":"tools/list","id":1}' | jq .
+
+# Test session reuse
+echo
+echo "Testing session reuse (second request)..."
+curl -s -X POST http://localhost:3000/mcp \
+  -H "Content-Type: application/json" \
+  -H "Authorization: Bearer $AUTH_TOKEN" \
+  -d '{"jsonrpc":"2.0","method":"get_database_statistics","id":2}' | jq .
+
+# Check health again to see session info
+echo
+echo "Checking health to see session info..."
+curl -s http://localhost:3000/health | jq .
+
+# Clean up
+echo
+echo "Stopping server..."
+kill $SERVER_PID 2>/dev/null || true
+wait $SERVER_PID 2>/dev/null || true
+
+echo
+echo "✅ Test complete! Check server.log for details."