feat(logging): implement structured logging system (#560)

api/middleware/errorHandler.js

@@ -3,13 +3,15 @@
  * Centralizes error handling and provides consistent error responses
  */
 
+const logger = require('../services/logger');
+
 const errorHandler = (err, req, res, next) => {
-  console.error('Error:', {
+  const log = req.log || logger;
+  log.error('unhandled_error', {
     message: err.message,
     stack: err.stack,
     url: req.url,
     method: req.method,
-    timestamp: new Date().toISOString(),
   });
 
   // Default error response

api/middleware/requestLogger.js

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: Apache-2.0
+/**
+ * Request logging middleware (#560)
+ *
+ * Logs every incoming request and outgoing response in structured JSON.
+ * Attaches a per-request child logger to req.log for use in route handlers.
+ */
+
+const logger = require('../services/logger');
+const { performance } = require('perf_hooks');
+
+function requestLogger(req, res, next) {
+  const start = performance.now();
+  const log = logger.forRequest(req);
+  req.log = log;
+
+  log.info('request', {
+    method: req.method,
+    url: req.originalUrl,
+    ip: req.ip,
+    userAgent: req.get('User-Agent'),
+  });
+
+  res.on('finish', () => {
+    const durationMs = (performance.now() - start).toFixed(2);
+    const level = res.statusCode >= 500 ? 'error' : res.statusCode >= 400 ? 'warn' : 'info';
+    log[level]('response', {
+      method: req.method,
+      url: req.originalUrl,
+      status: res.statusCode,
+      durationMs: parseFloat(durationMs),
+    });
+    logger.perf('http_request', parseFloat(durationMs), {
+      method: req.method,
+      route: req.route?.path || req.path,
+      status: res.statusCode,
+    });
+  });
+
+  next();
+}
+
+module.exports = requestLogger;