feat(obs, net): Add Tempo service and enable dual-stack listener (#192)

This commit introduces two key enhancements: the integration of Grafana Tempo for distributed tracing and the implementation of a dual-stack TCP listener for improved network compatibility.

- **Observability**:
  - Adds the `tempo` service to the `docker-compose.yml` observability stack.
  - Tempo is configured to collect and store traces, integrating with the existing OpenTelemetry setup.
  - A custom `tempo-entrypoint.sh` script is included to manage volume permissions on startup.

- **Networking**:
  - Modifies `http.rs` to support dual-stack (IPv4/IPv6) connections on a single socket.
  - By setting the `IPV6_V6ONLY` socket option to `false`, the server can now accept both IPv6 and IPv4-mapped IPv6 traffic, enhancing cross-platform support.

.docker/observability/grafana-datasources.yaml

@@ -0,0 +1,32 @@
+apiVersion: 1
+
+datasources:
+  - name: Prometheus
+    type: prometheus
+    uid: prometheus
+    access: proxy
+    orgId: 1
+    url: http://prometheus:9090
+    basicAuth: false
+    isDefault: false
+    version: 1
+    editable: false
+    jsonData:
+      httpMethod: GET
+  - name: Tempo
+    type: tempo
+    access: proxy
+    orgId: 1
+    url: http://tempo:3200
+    basicAuth: false
+    isDefault: true
+    version: 1
+    editable: false
+    apiVersion: 1
+    uid: tempo
+    jsonData:
+      httpMethod: GET
+      serviceMap:
+        datasourceUid: prometheus
+      streamingEnabled:
+        search: true