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/compose.yaml

@@ -0,0 +1,9 @@
+services:
+  lgtm:
+    image: grafana/otel-lgtm:latest
+    ports:
+      - "3000:3000"   # Grafana UI
+      - "4317:4317"   # OTLP gRPC ingest
+      - "4318:4318"   # OTLP HTTP ingest
+      - "9090:9090"   # Prometheus-compatible query API (bundled Prometheus)
+      - "3200:3200"   # Tempo query API (traces)