Implement n8n-MCP integration

This commit adds a complete integration between n8n workflow automation and the Model Context Protocol (MCP):

Features:
- MCP server that exposes n8n workflows as tools, resources, and prompts
- Custom n8n node for connecting to MCP servers from workflows
- Bidirectional bridge for data format conversion
- Token-based authentication and credential management
- Comprehensive error handling and logging
- Full test coverage for core components

Infrastructure:
- TypeScript/Node.js project setup with proper build configuration
- Docker support with multi-stage builds
- Development and production docker-compose configurations
- Installation script for n8n custom node deployment

Documentation:
- Detailed README with usage examples and API reference
- Environment configuration templates
- Troubleshooting guide

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

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

src/utils/logger.ts

@@ -0,0 +1,106 @@
+export enum LogLevel {
+  ERROR = 0,
+  WARN = 1,
+  INFO = 2,
+  DEBUG = 3,
+}
+
+export interface LoggerConfig {
+  level: LogLevel;
+  prefix?: string;
+  timestamp?: boolean;
+}
+
+export class Logger {
+  private config: LoggerConfig;
+  private static instance: Logger;
+
+  constructor(config?: Partial<LoggerConfig>) {
+    this.config = {
+      level: LogLevel.INFO,
+      prefix: 'n8n-mcp',
+      timestamp: true,
+      ...config,
+    };
+  }
+
+  static getInstance(config?: Partial<LoggerConfig>): Logger {
+    if (!Logger.instance) {
+      Logger.instance = new Logger(config);
+    }
+    return Logger.instance;
+  }
+
+  private formatMessage(level: string, message: string): string {
+    const parts: string[] = [];
+    
+    if (this.config.timestamp) {
+      parts.push(`[${new Date().toISOString()}]`);
+    }
+    
+    if (this.config.prefix) {
+      parts.push(`[${this.config.prefix}]`);
+    }
+    
+    parts.push(`[${level}]`);
+    parts.push(message);
+    
+    return parts.join(' ');
+  }
+
+  private log(level: LogLevel, levelName: string, message: string, ...args: any[]): void {
+    if (level <= this.config.level) {
+      const formattedMessage = this.formatMessage(levelName, message);
+      
+      switch (level) {
+        case LogLevel.ERROR:
+          console.error(formattedMessage, ...args);
+          break;
+        case LogLevel.WARN:
+          console.warn(formattedMessage, ...args);
+          break;
+        default:
+          console.log(formattedMessage, ...args);
+      }
+    }
+  }
+
+  error(message: string, ...args: any[]): void {
+    this.log(LogLevel.ERROR, 'ERROR', message, ...args);
+  }
+
+  warn(message: string, ...args: any[]): void {
+    this.log(LogLevel.WARN, 'WARN', message, ...args);
+  }
+
+  info(message: string, ...args: any[]): void {
+    this.log(LogLevel.INFO, 'INFO', message, ...args);
+  }
+
+  debug(message: string, ...args: any[]): void {
+    this.log(LogLevel.DEBUG, 'DEBUG', message, ...args);
+  }
+
+  setLevel(level: LogLevel): void {
+    this.config.level = level;
+  }
+
+  static parseLogLevel(level: string): LogLevel {
+    switch (level.toLowerCase()) {
+      case 'error':
+        return LogLevel.ERROR;
+      case 'warn':
+        return LogLevel.WARN;
+      case 'debug':
+        return LogLevel.DEBUG;
+      case 'info':
+      default:
+        return LogLevel.INFO;
+    }
+  }
+}
+
+// Create a default logger instance
+export const logger = Logger.getInstance({
+  level: Logger.parseLogLevel(process.env.LOG_LEVEL || 'info'),
+});