Each host adds AddOpenTelemetry().WithTracing with ASP.NET Core + HttpClient
auto-instrumentation and an OTLP exporter to Tempo; service name + endpoint from
OTEL_* env set per app service in compose. Since every cross-service call goes
through a typed HttpClient, traceparent propagates for free, so a request is one
connected trace (bff → domain/projection → acl → openzaak). /health is filtered
out. The exporter no-ops harmlessly when Tempo is unreachable (verified: domain
boots healthy with no collector).
refs #123
not
eho