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/tempo.yaml

@@ -0,0 +1,55 @@
+stream_over_http_enabled: true
+server:
+  http_listen_port: 3200
+  log_level: info
+
+query_frontend:
+  search:
+    duration_slo: 5s
+    throughput_bytes_slo: 1.073741824e+09
+    metadata_slo:
+      duration_slo: 5s
+      throughput_bytes_slo: 1.073741824e+09
+  trace_by_id:
+    duration_slo: 5s
+
+distributor:
+  receivers:
+    otlp:
+      protocols:
+        grpc:
+          endpoint: "tempo:4317"
+
+ingester:
+  max_block_duration: 5m # cut the headblock when this much time passes. this is being set for demo purposes and should probably be left alone normally
+
+compactor:
+  compaction:
+    block_retention: 1h # overall Tempo trace retention. set for demo purposes
+
+metrics_generator:
+  registry:
+    external_labels:
+      source: tempo
+      cluster: docker-compose
+  storage:
+    path: /var/tempo/generator/wal
+    remote_write:
+      - url: http://prometheus:9090/api/v1/write
+        send_exemplars: true
+  traces_storage:
+    path: /var/tempo/generator/traces
+
+storage:
+  trace:
+    backend: local # backend configuration to use
+    wal:
+      path: /var/tempo/wal # where to store the wal locally
+    local:
+      path: /var/tempo/blocks
+
+overrides:
+  defaults:
+    metrics_generator:
+      processors: [ service-graphs, span-metrics, local-blocks ] # enables metrics generator
+      generate_native_histograms: both