chore: archive observability-service-registry, track pi-map artifacts

- Archive the completed observability-service-registry SDD change into
  openspec/changes/archive/ (delivered across 5 slices; only
  jellyfin-service-registry remains active).
- Stop ignoring .pi-map.md / .pi-map.index.md so the navigation maps are
  versioned alongside the code, and add the regenerated map pairs repo-wide.

monitoring/grafana/.pi-map.md

@@ -0,0 +1,19 @@
+# monitoring/grafana
+dir: monitoring/grafana
+
+index: monitoring/grafana/.pi-map.index.md
+
+## role
+Provides centralized configuration for deploying and securing a Grafana monitoring dashboard instance.
+## files
+- grafana.ini | Grafana configuration file enabling OAuth authentication via Authentik, iframe embedding support, and role-based access control via group membership | dep: Authentik, Grafana, environment variables (GF_AUTH_GENERIC_OAUTH_*)
+## arch
+Declarative infrastructure configuration utilizing file-based static settings for OAuth2 (Authentik), role-based access control (RBAC), and UI embedding parameters.
+## tags
+grafana, authentik, configuration, enabling, oauth, authentication, iframe, embedding
+## symbols
+-
+## workflows
+-
+## dirty
+-