S-09b: Approval flow — temp admin endpoint + status transition to projection (#77)

## What & why

S-09b (#75, split from #10) — the **approval flow** that completes the walking skeleton. A behandelaar can now approve a submitted registration; the entry flips from `INGEDIEND` to `INGESCHREVEN` in the public register. Flow: `POST /registrations/{id}/approve` (domain) → ACL sets the zaak eindstatus (ZGW `/statussen`) → OpenZaak → NRC → event-subscriber → projection → openbaar.

## Changes (bottom-up, each red→green TDD)

- **Domain** — `RegistrationStatus.Ingeschreven` + `Registration.Approve()` (guards: opened zaak, only from INGEDIEND); `ApproveRegistration` use case (idempotent) + temp `POST /registrations/{id}/approve` endpoint; `IAclClient.ApproveZaakAsync`.
- **ACL** — resolves the zaaktype's **eindstatus** from the catalogus (`isEindstatus` / highest volgnummer) and POSTs a ZGW status; exposed as `POST /statussen`. Unit + real-OpenZaak integration test.
- **Event-subscriber** — binds NRC `hoofdObject`, projects a `status`/`create` as `INGESCHREVEN` keyed on the zaak (updates the existing row), **without reading OpenZaak** (§8.1). Retains the ZGW `resource` in the log (new column + EF migration) so a rebuild reproduces the status.
- **e2e** — extended: submit → public INGEDIEND → approve → public INGESCHREVEN.
- **Docs** — ADR-0011 (the two non-obvious decisions + the walking-skeleton assumption) + demo note.

## Key decisions (see ADR-0011)

- **ACL discovers the eindstatus** (chosen over injecting a statustype URL): no new config/seed plumbing, domain stays ZGW-ignorant.
- **Any post-creation status-set ⇒ INGESCHREVEN**: in the walking skeleton the only status ever set after creation is the approval, and the subscriber may not read ZGW — documented to tighten when more transitions arrive (S-12+).

## Verification

- All .NET unit suites green locally (domain 47, acl 11, event-subscriber 14, bff 16, acceptance 7); Release build + `dotnet format` clean.
- No new compose config (the eindstatus-discovery approach avoided it).
- The real-OpenZaak integration test (ACL status-set) and the full submit→approve→visible e2e run in CI `verify-stack` (live NRC→projection + selectielijst egress, not reproducible locally).

closes #75

Reviewed-on: #77

docs/architecture/adr-0011-approval-status-flow.md

@@ -0,0 +1,64 @@
+# ADR-0011: Approval sets the zaak eindstatus via the ACL and projects INGESCHREVEN from the notification alone
+
+- **Status:** Accepted
+- **Date:** 2026-07-13
+- **Deciders:** Respellion engineering
+- **Relates to:** S-09b (#75); split from S-09 (#10); builds on ADR-0001 (§8 loose coupling), ADR-0003 (ACL default-fill), ADR-0007 (OZ→NRC wiring), ADR-0008 (read projection), ADR-0009 (external-task worker)
+
+## Context
+
+The walking skeleton could submit a registration (INGEDIEND) and show it in the openbaar register,
+but nothing could **approve** it. S-09b adds a behandelaar approval that must make the entry publicly
+visible as a terminal status. There is no behandel-portal yet (S-12), so approval is triggered by a
+**temporary admin endpoint** on the Domain Service.
+
+Two decisions are non-obvious (§14) and cross service boundaries:
+
+1. **Who resolves the ZGW statustype?** Approval means "set the zaak to its final status", but the
+   domain must stay ZGW-ignorant (§8.1 — only the ACL talks to ZGW) and does not know statustype URLs.
+2. **How does the projection learn the new status?** The status is set in OpenZaak, which notifies over
+   NRC; the Event Subscriber projects it. But the subscriber **may not read OpenZaak** (§8.1), and an
+   NRC `status`/`create` notification's `resourceUrl` is the *status* resource, not the zaak, and does
+   not carry the statustype.
+
+## Decision
+
+**Approval flows Domain → ACL → OpenZaak → NRC → Event Subscriber → projection, using only the
+notification's own fields on the read side.**
+
+- **Domain.** `Registration.Approve()` advances INGEDIEND → INGESCHREVEN (requires an opened zaak; a
+  repeat is a no-op). The `ApproveRegistration` use case calls the ACL to set the zaak status, then
+  advances the aggregate. A temporary `POST /registrations/{id}/approve` endpoint drives it.
+- **ACL.** A new `POST /statussen` operation takes only the zaak URL. The ACL resolves the zaaktype's
+  **eindstatus** from the catalogus (`isEindstatus`, falling back to the highest `volgnummer`) and
+  POSTs a ZGW status against the zaak. The domain never names statustypen — the ACL owns the ZGW
+  translation (§8.1, ADR-0003).
+- **Event Subscriber.** It binds the NRC `hoofdObject` (always the zaak URL) and keys the projection on
+  it, so a `zaken`/`status`/`create` notification updates the **same** row the zaak-create created,
+  flipping it to INGESCHREVEN. It takes **any** status-create as the approval — in the walking skeleton
+  the only status ever set after creation is the approval — so it never has to read OpenZaak to learn
+  the statustype. The ZGW `resource` is retained in the notification log (new column) so a rebuild
+  reproduces the right status.
+
+## Consequences
+
+- The domain↔ACL boundary stays clean: the domain hands over a zaak URL and says "approve"; ZGW
+  statustype knowledge lives only in the ACL.
+- The projection remains rebuildable without OpenZaak (§8.1, ADR-0008): the log now records the ZGW
+  resource, which is all a rebuild needs to reproject the status.
+- The openbaar register shows real lifecycle: INGEDIEND on submit, INGESCHREVEN on approval.
+- **Walking-skeleton assumption:** "any status-create ⇒ INGESCHREVEN" holds only while approval is the
+  sole post-creation status transition. When more transitions arrive (beoordeling, afwijzing — S-12+),
+  the subscriber must distinguish statustypen. The honest options then are to carry the statustype
+  omschrijving in the notification `kenmerken`, or to have the ACL resolve it and re-notify — recorded
+  here so future-me revisits this rather than assuming it generalises.
+
+## Alternatives considered
+
+- **Inject the approved statustype URL into the ACL as config** (like the zaaktype URL). Rejected:
+  couples ACL config to seed output and adds compose/run-domain-check plumbing; runtime eindstatus
+  discovery keeps the ACL self-contained for one extra ZGW GET per approval.
+- **Have the Event Subscriber GET the status/statustype from OpenZaak** to map precisely. Rejected:
+  violates §8.1 (only the ACL talks to ZGW) and makes the projection depend on OpenZaak being up.
+- **Record the derived status in the notification log** instead of the ZGW resource. Rejected: the log
+  should retain notification *facts*, not projection semantics; the mapping stays in the projector.