feat(acl): resolve the zaaktype by identificatie, not a pinned URL (S-27, closes #113) (#118)

## What & why

The ACL was handed a **pinned zaaktype URL** (`Acl__Defaults__ZaaktypeUrl`) + informatieobjecttype URL. OpenZaak assigns those UUIDs at creation, so every stack had to seed the catalogus and then capture + inject the resulting URLs out of band (CI's `run-domain-check.sh`; the local `local-seed`→`acl.env` bootstrap from ADR-0020). Brittle, and a stale/placeholder URL failed opaquely (OpenZaak 400).

Now **the ACL resolves them itself** from OpenZaak's Catalogi API by stable business key:
- config `ZaaktypeIdentificatie` (`BIG-REGISTRATIE`) / `InformatieobjecttypeOmschrijving` (`Diploma`);
- a `CachedZaaktypeCatalog` resolves **lazily on first use** and caches (success only, so a pre-publish miss is retried — no startup ordering coupling);
- a clear "No published … found" error replaces the opaque placeholder 400.

Design in **ADR-0021** (proposed in #117).

Closes #113
Closes #117

## Consequences (the payoff)

No stack captures/injects a server-assigned URL any more — `docker-compose.yml`/`.local.yml`, `run-domain-check.sh` and `local-seed` all drop it; the local `acl.env` shrinks to a single line.

**One thing S-27 can't remove** (confirmed empirically during this work): OpenZaak validates the `zaaktype` field on zaak-create with Django's URLValidator and **rejects a single-label host** (`http://openzaak:8000/…` → `zaaktype: bad-url`). So the ACL's **base URL** must still point at a URL-valid host (a container IP); that base-URL injection from ADR-0020 stays (local `acl.env` now carries only it; CI keeps `ACL_OPENZAAK_BASEURL`). ADR-0021 records this.

## Definition of Done

- [x] Linked issues (#113 slice, #117 adr-proposal).
- [x] TDD — resolver + gateway-lookup unit tests, updated `AclService` tests (50 unit tests green).
- [x] Implementation makes them pass; refactor of both compose stacks + verify scripts follows.
- [x] Conventional Commits referencing #113.
- [ ] CI green — see below.
- [x] `docker compose up` reaches green health — verified: fresh `make local` + `make verify-local` green with **no zaaktype-URL injection**; `acl.env` is base-URL-only.
- [x] Docs — ADR-0021 + demo-script S-27 note.
- [x] ADR added (ADR-0021).
- [x] Demo note appended.

## Verification done locally

- **50 unit tests** pass (resolver resolve/cache/retry-on-failure; gateway match/miss/blank-key; all `AclService` paths).
- **6 ACL integration tests** pass against a live seeded OpenZaak — incl. resolving the zaaktype + Diploma iot by business key, and a clear error for an unknown identificatie.
- **Fresh `make local` + `make verify-local`**: full flow (submit → werkbak → openbaar) green; `acl.env` = `Acl__OpenZaak__BaseUrl` only.
- `make lint` clean; ACL mutation ratchet run locally (see checks).

## Notes for reviewers

- `IZaakGateway` gains two resolve methods; `AclService` depends on the new `IZaaktypeCatalog` (singleton, so the cache persists).
- Supersedes the pinned-URL mechanism; ADR-0021 documents that ADR-0020's `seed-env`/entrypoint shim are **simplified** (base-URL only), not deleted, because of the URLValidator constraint above.

Reviewed-on: #118

infra/docker-compose.local.yml

@@ -315,21 +315,22 @@ services:
       context: ../services/acl
       dockerfile: Dockerfile
     image: register-referentie/acl:dev
-    # The base/zaaktype/informatieobjecttype below are PLACEHOLDERS. The real, server-assigned
-    # values are written by the local-seed one-shot into seed-env:/seed/acl.env, which the entrypoint
-    # sources (set -a) so they override these before the app starts (S-B04, #110, ADR-0020). Sourcing
-    # a runtime-generated env file is why we override the entrypoint here rather than use `env_file:`
-    # (which compose reads at parse time, before the seed has run).
+    # The ACL discovers its zaaktype + informatieobjecttype URLs from the Catalogi API by the business
+    # keys below (S-27, ADR-0021), so no URL is injected. It still needs its OpenZaak BaseUrl pointed at
+    # a URL-valid host (OpenZaak rejects a single-label host like `openzaak` on zaak-create), so the
+    # local-seed one-shot writes that IP base into seed-env:/seed/acl.env, which the entrypoint sources
+    # (set -a) before the app starts. A runtime-generated env file is why we override the entrypoint here
+    # rather than use `env_file:` (which compose reads at parse time, before the seed has run).
     entrypoint: ["/bin/sh", "-c", "set -a; . /seed/acl.env; set +a; exec dotnet Acl.Api.dll"]
     environment:
-      Acl__OpenZaak__BaseUrl: http://openzaak:8000/
+      Acl__OpenZaak__BaseUrl: http://openzaak:8000/   # placeholder; seed-env/acl.env supplies the IP base
       Acl__OpenZaak__ClientId: big-reference-seed
       Acl__OpenZaak__Secret: insecure-dev-secret-change-me
       Acl__Defaults__Bronorganisatie: "517439943"
       Acl__Defaults__VerantwoordelijkeOrganisatie: "517439943"
       Acl__Defaults__Vertrouwelijkheidaanduiding: openbaar
-      Acl__Defaults__ZaaktypeUrl: http://openzaak:8000/catalogi/api/v1/zaaktypen/00000000-0000-0000-0000-000000000000
-      Acl__Defaults__InformatieobjecttypeUrl: http://openzaak:8000/catalogi/api/v1/informatieobjecttypen/00000000-0000-0000-0000-000000000000
+      Acl__Defaults__ZaaktypeIdentificatie: BIG-REGISTRATIE
+      Acl__Defaults__InformatieobjecttypeOmschrijving: Diploma
     ports:
       - "8100:8080"
     volumes: