Add OpenTelemetry tracing and log export via OTLP

Shared telemetry init module in compliance-core (behind `telemetry` feature)
sets up OTLP/gRPC export for traces and logs when OTEL_EXPORTER_OTLP_ENDPOINT
is set. Falls back to console-only output when unset.

Both agent and dashboard now use the shared init. Docker Compose includes
an OTel Collector service with a config template for SigNoz, Grafana
Tempo/Loki, Jaeger, etc.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compliance-dashboard/Cargo.toml

@@ -18,6 +18,7 @@ server = [
     "dioxus/router",
     "dioxus/fullstack",
     "compliance-core/mongodb",
+    "compliance-core/telemetry",
     "dep:axum",
     "dep:mongodb",
     "dep:reqwest",