arch(infra): ADR-0007 + runbooks for the OZ→NRC notification wiring (refs #56)

Records the wiring decision (AC-delegated auth, required celery-beat) and the two
non-obvious gotchas: single-label hosts aren't URL-valid (reach services by IP) and
abonnement callbacks must enforce auth. Documents the new notifications CI job.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/runbooks/ci.md

@@ -18,6 +18,7 @@ and CI cannot drift:
 | `unit` | `make unit` → `dotnet test … -c Release --filter "Category!=Integration"` | .NET 10 SDK |
 | `mutation` | `make mutation` → `dotnet tool restore` → `dotnet stryker` (ACL); uploads the HTML report as an artifact | .NET 10 SDK |
 | `integration` | `make integration` → `infra/run-integration.sh`: OpenZaak up → seed a **published** BIG zaaktype + run `Acl.IntegrationTests` **as containers inside the compose network** → tear down | container engine + egress (base images, nuget, `selectielijst.openzaak.nl`) |
+| `notifications` | `make verify-notifications` → bring up OpenZaak + NRC → seed → assert a zaak-create notification reaches a subscriber (containers on the network) → tear down | container engine + egress (base images, `selectielijst.openzaak.nl`) |
 | `compose-smoke` | `make smoke` → seed config volumes → `up -d` (full stack) → `up --wait` durable services → `down` | container engine + compose v2 |
 
 > **The `integration` job needs no `setup-dotnet`.** dotnet runs inside the test