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/Cargo.toml

@@ -7,7 +7,7 @@ edition = "2021"
 workspace = true
 
 [dependencies]
-compliance-core = { workspace = true, features = ["mongodb"] }
+compliance-core = { workspace = true, features = ["mongodb", "telemetry"] }
 compliance-graph = { path = "../compliance-graph" }
 compliance-dast = { path = "../compliance-dast" }
 serde = { workspace = true }