Enrich 500 error logs with request context and actual error messages

- pino-http customErrorMessage now includes the real error message
- customProps includes reqBody, reqParams, reqQuery, and routePath for 4xx/5xx
- Error handler logs full request context (body, params, query) for both
  HttpError 500s and unhandled errors

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/middleware/logger.ts

@@ -52,10 +52,28 @@ export const httpLogger = pinoHttp({
   customSuccessMessage(req, res) {
     return `${req.method} ${req.url} ${res.statusCode}`;
   },
-  customErrorMessage(req, res) {
-    return `${req.method} ${req.url} ${res.statusCode}`;
+  customErrorMessage(req, res, err) {
+    const errMsg = err?.message || (res as any).err?.message || "unknown error";
+    return `${req.method} ${req.url} ${res.statusCode} — ${errMsg}`;
   },
-  customProps() {
+  customProps(req, res) {
+    if (res.statusCode >= 400) {
+      const props: Record<string, unknown> = {};
+      const { body, params, query } = req as any;
+      if (body && typeof body === "object" && Object.keys(body).length > 0) {
+        props.reqBody = body;
+      }
+      if (params && typeof params === "object" && Object.keys(params).length > 0) {
+        props.reqParams = params;
+      }
+      if (query && typeof query === "object" && Object.keys(query).length > 0) {
+        props.reqQuery = query;
+      }
+      if ((req as any).route?.path) {
+        props.routePath = (req as any).route.path;
+      }
+      return props;
+    }
     return {};
   },
 });