feat(observability): add phase9 health, readiness, metrics, request tracing, and simulator ops checks

Backend/observability/metrics.ts

@@ -0,0 +1,15 @@
+const counters = new Map<string, number>();
+
+export const incrementMetric = (name: string, value = 1): void => {
+  counters.set(name, (counters.get(name) ?? 0) + value);
+};
+
+export const getAllMetrics = (): Record<string, number> => {
+  const result: Record<string, number> = {};
+
+  for (const [key, value] of counters.entries()) {
+    result[key] = value;
+  }
+
+  return result;
+};