feat(08-01): Health monitoring & logging infrastructure

- Set up Winston structured logging with console and file outputs
- Create GET /api/health endpoint with uptime, database status, response times
- Add request logging middleware (method, path, statusCode, duration)
- Create health monitoring module with database connectivity checks
- Log all HTTP requests with timing information
- Log auth events (login, register) and data modifications
- Replace console.log/error with structured logger calls
- Update backend README with logging configuration documentation
- Add tests for health endpoint and logging middleware
- Logs directory: logs/combined.log and logs/error.log

Deliverables met:
✓ Structured logging (Winston) integrated
✓ Enhanced health endpoint with uptime & database info
✓ Request logging middleware attached to all routes
✓ Comprehensive logging documentation in README.md
✓ Tests passing for health and logging functionality
✓ All critical operations logged with context

backend/src/middleware/requestLogger.js

@@ -0,0 +1,33 @@
+const logger = require('../utils/logger');
+
+/**
+ * Request Logging Middleware
+ * Logs HTTP method, path, status code, and request duration
+ */
+function requestLoggerMiddleware(req, res, next) {
+  const startTime = Date.now();
+  const originalSend = res.send;
+
+  // Override send method to capture response
+  res.send = function (data) {
+    const duration = Date.now() - startTime;
+    const statusCode = res.statusCode;
+    
+    // Log request details
+    logger.info('HTTP Request', {
+      method: req.method,
+      path: req.path,
+      statusCode: statusCode,
+      duration: `${duration}ms`,
+      ip: req.ip,
+      userAgent: req.get('user-agent')
+    });
+
+    // Call original send method
+    return originalSend.call(this, data);
+  };
+
+  next();
+}
+
+module.exports = requestLoggerMiddleware;