added stack trace to some logging

backend/middleware/apiLogger.js

@@ -36,6 +36,34 @@ const apiLogger = (req, res, next) => {
       userId: req.user?.id || 'anonymous'
     };
 
+    // Parse response body for error responses to include error details
+    if (res.statusCode >= 400) {
+      let errorDetails = null;
+      if (body) {
+        try {
+          const parsed = typeof body === 'string' ? JSON.parse(body) : body;
+          // Extract error message, validation errors, or full response
+          errorDetails = {
+            error: parsed.error || parsed.message || null,
+            errors: parsed.errors || null, // validation errors array
+            details: parsed.details || null
+          };
+          // Remove null values
+          Object.keys(errorDetails).forEach(key => {
+            if (errorDetails[key] === null) delete errorDetails[key];
+          });
+          if (Object.keys(errorDetails).length > 0) {
+            responseData.errorDetails = errorDetails;
+          }
+        } catch (e) {
+          // Body is not JSON, include as string (truncated)
+          if (typeof body === 'string' && body.length > 0) {
+            responseData.errorDetails = { raw: body.substring(0, 500) };
+          }
+        }
+      }
+    }
+
     if (res.statusCode >= 400 && res.statusCode < 500) {
       // Don't log 401s for /users/profile - these are expected auth checks
       if (!(res.statusCode === 401 && req.url === '/profile')) {