feat(portal-beheer): beheer portal + read-only catalogus viewer (closes #130) (#133)

## What & why

S-15a, the first of the S-15 (#16) split. A new **beheer** portal (medewerker realm, like behandel) shows the ZTC catalogus — the published zaaktypen — **read-only**. A beheerder logs in and sees the seeded BIG-REGISTRATIE zaaktype.

Closes #130

### The vertical

portal → BFF `GET /beheer/catalogi/zaaktypen` (medewerker realm + `beheerder` role) → ACL `GET /catalogi/zaaktypen` → ZGW Catalogi API.

- **ACL**: new read-only `GET /catalogi/zaaktypen` listing published zaaktypen (reuses the ADR-0021 Catalogi client; public-safe `identificatie`/`omschrijving`).
- **BFF**: new typed `IAclClient` + `Downstream:Acl:BaseUrl`, and `GET /beheer/catalogi/zaaktypen` behind a new `beheerder` policy (reuses the medewerker bearer scheme + realm-role lifting). OpenAPI spec + generated Angular client regenerated.
- **Keycloak**: `beheerder` realm role + `bram-beheerder` test user in the medewerker realm.
- **Frontend**: new `apps/beheer` Angular app (copied from behandel) with a read-only catalogus page; `SECURE_API_ROUTES=['/beheer/']`.
- **Infra**: `beheer` compose service (port 8143), added to `WAIT_SVCS` + CI log-dump; a Playwright e2e (beheerder login → catalogus shows BIG-REGISTRATIE).

### New boundary → ADR-0025

The BFF now reaches the **ACL directly** for the catalogus read — a new service-to-service edge (§14). The catalogus is neither a domain nor a projection concern, and §8.1 means only the ACL may read ZGW; routing through the domain would pollute it with a non-domain passthrough. §8.1/§8.3 stay intact. Recorded in **ADR-0025**.

## Definition of Done

- [x] Failing test committed before each implementation (red→green per layer: ACL, BFF, frontend).
- [x] Conventional Commits referencing #130.
- [ ] CI green — pending Gitea Actions run.
- [x] `docker compose up` brings up `beheer` (health-gated in `WAIT_SVCS`).
- [x] Docs — ADR-0025 + demo-script S-15a note.
- [x] Demo note in `docs/demo-script.md`.

## Verified locally

lint (`dotnet format`) ✓ · .NET unit (Acl 57 / Big 152 / EventSubscriber 19 / Bff 40) ✓ · frontend lint+test (8 projects) ✓ · frontend build (4 apps) ✓. Mutation ratchet: added a gateway unit test for the new `ListZaaktypenAsync` mapping so the ACL score holds. verify-stack (compose smoke + e2e) runs in CI.

## Notes for reviewers

- The BFF drops the ZGW URL from `BeheerZaaktype` (public-safe: identificatie + omschrijving only).
- The catalogus e2e asserts on the stable seeded `BIG-REGISTRATIE` (not a per-test reference), safe on the shared verify stack.
- Follow-ups: **S-15b** (#131) default-fill CRUD, **S-15c** (#132) medewerker-realm MFA.

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #133

docs/demo-script.md

@@ -5,6 +5,32 @@ copy-pasteable walkthrough against a local `make up` stack.
 
 ---
 
+## S-15a — Beheer-portal: read-only catalogus viewer (#130, ADR-0025)
+
+**Outcome:** a new **beheer** portal (medewerker realm, like behandel) shows the ZTC catalogus —
+the published zaaktypen — **read-only**. A beheerder logs in and sees the seeded BIG-REGISTRATIE
+zaaktype. The read path is portal → BFF `GET /beheer/catalogi/zaaktypen` (medewerker realm +
+`beheerder` role) → ACL `GET /catalogi/zaaktypen` → ZGW Catalogi API. The BFF reaches the ACL
+directly (ADR-0025); managing the default-fill config (S-15b) and MFA (S-15c) come next.
+
+```bash
+make up
+# 1. Log in as bram-beheerder / test123 → the catalogus lists the published zaaktypen.
+open http://localhost:8143
+#
+# 2. Automated (a CI verify-stack e2e): a beheerder logs in and sees BIG-REGISTRATIE.
+make verify-e2e        # → catalogus.spec: "a beheerder sees the published zaaktypen in the catalogus"
+#
+# 3. The BFF endpoint is behind the beheerder role — a plain behandelaar gets 403 (BFF unit tests):
+#    Bff.Tests → BeheerEndpointTests.
+```
+
+**Auth:** the `beheerder` realm role + `bram-beheerder` user live in the medewerker realm
+(`infra/keycloak/realms/medewerker-realm.json`); the BFF reuses the medewerker bearer scheme and its
+realm-role lifting, requiring `beheerder` rather than `behandelaar`.
+
+---
+
 ## S-16c — Prometheus metrics + golden-signal Grafana dashboard (#124, ADR-0023)
 
 **Outcome:** the five .NET services now expose OpenTelemetry metrics in Prometheus format at `/metrics`