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-agent/src/main.rs

@@ -1,5 +1,3 @@
-use tracing_subscriber::EnvFilter;
-
 mod agent;
 mod api;
 mod config;
@@ -15,14 +13,10 @@ mod webhooks;
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    tracing_subscriber::fmt()
-        .with_env_filter(
-            EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info")),
-        )
-        .init();
-
     dotenvy::dotenv().ok();
 
+    let _telemetry_guard = compliance_core::telemetry::init_telemetry("compliance-agent");
+
     tracing::info!("Loading configuration...");
     let config = config::load_config()?;