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-core/src/lib.rs

@@ -1,6 +1,8 @@
 pub mod config;
 pub mod error;
 pub mod models;
+#[cfg(feature = "telemetry")]
+pub mod telemetry;
 pub mod traits;
 
 pub use config::{AgentConfig, DashboardConfig};