feat: Add Scanner CI runner and related artifacts

- Implemented `run-scanner-ci.sh` to build and run tests for the Scanner solution with a warmed NuGet cache.
- Created `excititor-vex-traces.json` dashboard for monitoring Excititor VEX observations.
- Added Docker Compose configuration for the OTLP span sink in `docker-compose.spansink.yml`.
- Configured OpenTelemetry collector in `otel-spansink.yaml` to receive and process traces.
- Developed `run-spansink.sh` script to run the OTLP span sink for Excititor traces.
- Introduced `FileSystemRiskBundleObjectStore` for storing risk bundle artifacts in the filesystem.
- Built `RiskBundleBuilder` for creating risk bundles with associated metadata and providers.
- Established `RiskBundleJob` to execute the risk bundle creation and storage process.
- Defined models for risk bundle inputs, entries, and manifests in `RiskBundleModels.cs`.
- Implemented signing functionality for risk bundle manifests with `HmacRiskBundleManifestSigner`.
- Created unit tests for `RiskBundleBuilder`, `RiskBundleJob`, and signing functionality to ensure correctness.
- Added filesystem artifact reader tests to validate manifest parsing and artifact listing.
- Included test manifests for egress scenarios in the task runner tests.
- Developed timeline query service tests to verify tenant and event ID handling.

docs/modules/export-center/operations/dashboards/export-center-observability.json

@@ -0,0 +1,6 @@
+{
+  "_note": "Placeholder Grafana dashboard stub for Export Center. Replace panels when metrics endpoints are available; keep offline-import friendly.",
+  "schemaVersion": 39,
+  "title": "Export Center Observability (stub)",
+  "panels": []
+}