Initial commit: Telegram Management System

Full-stack web application for Telegram management
- Frontend: Vue 3 + Vben Admin
- Backend: NestJS
- Features: User management, group broadcast, statistics

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

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

marketing-agent/services/ab-testing/src/utils/logger.js

@@ -0,0 +1,49 @@
+import winston from 'winston';
+import { config } from '../config/index.js';
+
+const { combine, timestamp, json, printf, colorize } = winston.format;
+
+// Custom format for console output
+const consoleFormat = printf(({ level, message, timestamp, ...meta }) => {
+    const metaStr = Object.keys(meta).length ? ` ${JSON.stringify(meta)}` : '';
+    return `${timestamp} [${level}]: ${message}${metaStr}`;
+});
+
+// Create logger
+export const logger = winston.createLogger({
+    level: config.logging.level,
+    format: combine(
+        timestamp(),
+        json()
+    ),
+    transports: [
+        // Console transport
+        new winston.transports.Console({
+            format: combine(
+                colorize(),
+                timestamp({ format: 'YYYY-MM-DD HH:mm:ss' }),
+                consoleFormat
+            )
+        }),
+        // File transport
+        new winston.transports.File({
+            filename: config.logging.file,
+            format: combine(
+                timestamp(),
+                json()
+            )
+        })
+    ]
+});
+
+// Add error file transport in production
+if (config.env === 'production') {
+    logger.add(new winston.transports.File({
+        filename: 'logs/error.log',
+        level: 'error',
+        format: combine(
+            timestamp(),
+            json()
+        )
+    }));
+}