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

services/bff/Bff.Tests/BffFactory.cs

@@ -23,6 +23,7 @@ internal sealed class BffFactory : WebApplicationFactory<Program>
 
     public FakeDomainClient Domain { get; } = new();
     public FakeProjectionClient Projection { get; } = new();
+    public FakeAclClient Acl { get; } = new();
 
     private static void ValidateWithTestKey(IServiceCollection services, string scheme) =>
         services.Configure<JwtBearerOptions>(scheme, options =>
@@ -54,11 +55,13 @@ internal sealed class BffFactory : WebApplicationFactory<Program>
         builder.UseSetting("Keycloak:MedewerkerAuthority", "https://keycloak.invalid/realms/medewerker");
         builder.UseSetting("Downstream:Domain:BaseUrl", "http://domain.invalid/");
         builder.UseSetting("Downstream:Projection:BaseUrl", "http://projection.invalid/");
+        builder.UseSetting("Downstream:Acl:BaseUrl", "http://acl.invalid/");
 
         builder.ConfigureTestServices(services =>
         {
             services.AddSingleton<IDomainClient>(Domain);
             services.AddSingleton<IProjectionClient>(Projection);
+            services.AddSingleton<IAclClient>(Acl);
 
             // Both realms validate locally against the test key (no live Keycloak). The medewerker
             // scheme keeps its OnTokenValidated role-lifting from Program.cs — only the validation
@@ -138,3 +141,12 @@ internal sealed class FakeProjectionClient : IProjectionClient
     public Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default)
         => Task.FromResult<IReadOnlyList<ProjectionEntry>>(Entries);
 }
+
+/// <summary>Serves a configurable set of catalogus zaaktypen (beheer viewer, S-15a).</summary>
+internal sealed class FakeAclClient : IAclClient
+{
+    public List<BeheerZaaktype> Zaaktypen { get; } = [];
+
+    public Task<IReadOnlyList<BeheerZaaktype>> GetZaaktypenAsync(CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<BeheerZaaktype>>(Zaaktypen);
+}