Add observability: real OTLP metrics/traces to grafana/otel-lgtm, Docker Compose auto-wiring, and a dual-version (Boot 4.0 vs 4.1) proof of the new OTEL_* env var support

Companion module for the rewritten ankurm.com Prometheus/Grafana monitoring post. Verified
against a real running grafana/otel-lgtm container (not mocked): 8 real requests produce a real
orders_placed_total metric queried back from the bundled Prometheus-compatible API with zero
management.otlp.* properties, auto-wired entirely by Boot's Docker Compose service-connection
detection. Two real findings surfaced along the way and documented rather than smoothed over:
@Observed silently produces no span without an explicit ObservedAspect bean (AspectJ weaving
alone is not sufficient, despite Micrometer Tracing being active), and OTEL_EXPORTER_OTLP_ENDPOINT
already worked on Boot 4.0 via Micrometer's own OtlpConfig fallback -- what's actually new in 4.1
is the rest of the standard OTEL_* surface (verified with OTEL_METRIC_EXPORT_INTERVAL against
identical source compiled on both Boot 4.0.8 and 4.1.1).

Also fixes the root README's module table, which was missing a row for
resilience4j-circuit-breaker (added in a previous commit but never indexed here).

observability/docs/output/01-metrics-and-traces-in-lgtm.txt

@@ -0,0 +1,29 @@
+8 real requests sent to the running app:
+  $ for i in $(seq 1 8); do curl -s -X POST "http://localhost:8080/orders/$i"; done
+
+Queried straight from the real Prometheus-compatible API bundled inside the grafana/otel-lgtm
+container -- not the app's own /actuator endpoint, not a mock:
+
+  $ curl -s "http://localhost:9090/api/v1/query?query=orders_placed_total"
+  {
+    "status": "success",
+    "data": {
+      "resultType": "vector",
+      "result": [
+        {
+          "metric": {
+            "__name__": "orders_placed_total",
+            "application": "order-service",
+            "channel": "web",
+            "job": "order-service",
+            "service_name": "order-service"
+          },
+          "value": [1789722945.151, "8"]
+        }
+      ]
+    }
+  }
+
+Every one of the 8 POSTs landed as a real OTLP metric, pushed over the network, through the
+Docker Compose auto-wired endpoint, and queried back out of the real Prometheus-compatible
+backend Grafana LGTM bundles.