feat: enhance security logging and ensure rate limit blocks are properly tracked

- Add comprehensive logging for rate limit blocks with full request details
  - IP address (with proper proxy detection), user agent, headers, timestamps
  - Rate limit info (current count, limit, remaining, reset time)
  - Separate tracking for auth vs general endpoints

- Enhance authentication failure logging
  - JWT validation failures with detailed error info
  - Admin auth attempts without token
  - Failed token validation with user context
  - All events include IP, path, method, user agent

- Improve Winston logger configuration for production
  - Add automatic log rotation (10MB errors, 50MB combined)
  - Create separate security.log for auth/rate limit events
  - Ensure logs directory exists automatically
  - Add structured JSON format for log aggregation
  - Support container logging with LOG_TO_CONSOLE env var

- Create comprehensive documentation
  - Security logging guide with examples
  - Monitoring recommendations
  - Configuration reference

- Add test script to verify logging functionality

All rate limit settings remain configurable via admin panel:
- Window duration, max requests, auth limits
- Skip authenticated requests option
- Public endpoints only option

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

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

backend/src/utils/formatters.js

@@ -0,0 +1,40 @@
+/**
+ * Formatters for email content and other text transformations
+ */
+
+/**
+ * Convert plain text line breaks to HTML line breaks
+ * @param {string} text - The text to format
+ * @returns {string} - Text with HTML line breaks
+ */
+function nl2br(text) {
+  if (!text) return '';
+  
+  // Normalize line endings
+  text = text.replace(/\r\n/g, '\n').replace(/\r/g, '\n');
+  
+  // Convert newlines to <br> tags
+  return text
+    .split('\n')
+    .map(line => line.trim())
+    .filter(line => line.length > 0)
+    .join('<br />');
+}
+
+/**
+ * Format welcome message for email templates
+ * @param {string} message - The welcome message
+ * @returns {string} - Formatted message for HTML emails
+ */
+function formatWelcomeMessage(message) {
+  if (!message || message.trim() === '') {
+    return '';
+  }
+  
+  return nl2br(message);
+}
+
+module.exports = {
+  nl2br,
+  formatWelcomeMessage
+};

backend/src/utils/logger.js

@@ -1,31 +1,98 @@
 const winston = require('winston');
 const path = require('path');
+const fs = require('fs');
+
+// Ensure logs directory exists
+const logDir = path.join(__dirname, '../../logs');
+if (!fs.existsSync(logDir)) {
+  fs.mkdirSync(logDir, { recursive: true });
+}
+
+// Custom format for production logs
+const productionFormat = winston.format.combine(
+  winston.format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss.SSS' }),
+  winston.format.errors({ stack: true }),
+  winston.format.json(),
+  winston.format.printf(info => {
+    // Ensure all security events are properly formatted
+    if (info.level === 'warn' && (info.message.includes('rate limit') || 
+                                   info.message.includes('auth') ||
+                                   info.message.includes('login') ||
+                                   info.message.includes('JWT'))) {
+      return JSON.stringify({
+        timestamp: info.timestamp,
+        level: info.level,
+        message: info.message,
+        security: true,
+        ...info
+      });
+    }
+    return JSON.stringify(info);
+  })
+);
 
 const logger = winston.createLogger({
   level: process.env.LOG_LEVEL || 'info',
-  format: winston.format.combine(
-    winston.format.timestamp(),
-    winston.format.errors({ stack: true }),
-    winston.format.json()
-  ),
+  format: productionFormat,
   transports: [
     new winston.transports.File({ 
-      filename: path.join(__dirname, '../../logs/error.log'), 
-      level: 'error' 
+      filename: path.join(logDir, 'error.log'), 
+      level: 'error',
+      maxsize: 10 * 1024 * 1024, // 10MB
+      maxFiles: 5,
+      tailable: true
     }),
     new winston.transports.File({ 
-      filename: path.join(__dirname, '../../logs/combined.log') 
+      filename: path.join(logDir, 'combined.log'),
+      maxsize: 50 * 1024 * 1024, // 50MB
+      maxFiles: 10,
+      tailable: true
+    }),
+    // Separate security log for authentication and rate limiting
+    new winston.transports.File({
+      filename: path.join(logDir, 'security.log'),
+      level: 'warn',
+      maxsize: 20 * 1024 * 1024, // 20MB
+      maxFiles: 10,
+      tailable: true,
+      format: winston.format.combine(
+        winston.format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss.SSS' }),
+        winston.format.json(),
+        winston.format.printf(info => {
+          // Only log security-related warnings
+          if (info.message.includes('rate limit') || 
+              info.message.includes('auth') ||
+              info.message.includes('login') ||
+              info.message.includes('JWT') ||
+              info.message.includes('lockout') ||
+              info.message.includes('suspicious')) {
+            return JSON.stringify(info);
+          }
+          return null;
+        })
+      )
     })
-  ]
+  ].filter(Boolean)
 });
 
+// Add console logging for non-production environments
 if (process.env.NODE_ENV !== 'production') {
   logger.add(new winston.transports.Console({
     format: winston.format.combine(
       winston.format.colorize(),
-      winston.format.simple()
+      winston.format.timestamp({ format: 'HH:mm:ss' }),
+      winston.format.printf(info => {
+        return `[${info.timestamp}] ${info.level}: ${info.message} ${info.stack || ''}`;
+      })
     )
   }));
+} else {
+  // In production, also log to console for container environments
+  if (process.env.LOG_TO_CONSOLE === 'true') {
+    logger.add(new winston.transports.Console({
+      format: productionFormat
+    }));
+  }
 }
 
 module.exports = logger;