[claude] API observability — structured logging + /api/metrics endpoint (#57) (#87)

artifacts/api-server/src/middlewares/response-time.ts

@@ -1,6 +1,7 @@
 import type { Request, Response, NextFunction } from "express";
 import { makeLogger } from "../lib/logger.js";
 import { latencyHistogram } from "../lib/histogram.js";
+import { requestCounters } from "../lib/request-counters.js";
 
 const logger = makeLogger("http");
 
@@ -13,8 +14,10 @@ export function responseTimeMiddleware(req: Request, res: Response, next: NextFu
     const routeKey = `${req.method} ${route ?? req.path}`;
 
     latencyHistogram.record(routeKey, durationMs);
+    requestCounters.record(res.statusCode);
 
     logger.info("request", {
+      request_id: res.locals["requestId"] ?? null,
       method:      req.method,
       path:        req.path,
       route:       route ?? null,