feat(acl): diploma upload stored in the ZGW Documenten API (S-10b, closes #103) (#108)

## What & why

S-10b: the self-service **diploma upload** is now real. After submitting, the citizen picks a PDF and
uploads it; the portal base64-encodes it client-side → BFF → domain → **ACL**, which stores it in the
ZGW **Documenten (DRC) API** as an `enkelvoudiginformatieobject` and relates it to the zaak, then the
`WachtOpDocumenten` wait completes and the case advances to beoordeling. Per §8.1 only the ACL talks to
ZGW.

Closes #103

Mechanism in **ADR-0018** (proposal #107). Builds on S-10a (#102). The zaak-close-on-expiry item is
carved to **#106 (S-10c)**.

## Definition of Done

- [x] Linked Gitea issue (above).
- [x] Failing test committed before the implementation (red→green per layer).
- [x] Conventional Commits referencing the issue (`refs #103`).
- [ ] CI green — all Gitea Actions jobs (pending on this PR).
- [x] `docker compose up` health unaffected (ACL boots on a placeholder informatieobjecttype URL; the real one is injected by verify-domain).
- [x] Docs updated (ADR-0018, demo-script, BACKLOG + S-10c).
- [x] ADR added (`docs/architecture/adr-0018-diploma-upload-via-acl-documenten.md`).
- [x] Demo note in `docs/demo-script.md`.

## Notes for reviewers

- **ACL** (`OpenZaakGateway.StoreDocumentAsync` + `AclService.StoreDiplomaAsync` + `POST /documenten`) reuses the existing gateway patterns (ZGW Bearer, buffered non-chunked body, **no CRS** — Documenten isn't geo). Unit-tested via the stub handler; an **integration test** stores a real document against live OpenZaak (verify-acl).
- **Transport:** base64 JSON on every hop (portal encodes client-side) — I deviated from proposal #107's multipart to keep one contract shape and avoid `IFormFile`/antiforgery/multipart-client plumbing; fine at diploma size (ADR-0018 §Alternatives).
- **Infra:** `seed_catalogus.py` seeds + publishes a "Diploma" `informatieobjecttype` and relates it to the zaaktype (while both concept); `verify-domain` injects its URL into the ACL. No new ZGW scopes (seed applicatie has `heeft_alle_autorisaties`).
- **e2e:** uploads a real PDF (`setInputFiles`) after the openbaar INGEDIEND row confirms the zaak is open (so storage doesn't race the OpenZaak worker).
- **Scope boundary:** the ZGW zaak is not set to a cancellation status on 30-day expiry — that's #106 (S-10c).

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

Reviewed-on: #108

libs/api-client/src/lib/generated/bff-api.ts

@@ -35,6 +35,14 @@ export interface OpenbaarEntry {
   reference: string | null;
 }
 
+export interface ProvideDocumentsRequest {
+  contentBase64: string;
+  /** @nullable */
+  fileName?: string | null;
+  /** @nullable */
+  contentType?: string | null;
+}
+
 export interface SubmitAccepted {
   registrationId: string;
   status: string;
@@ -226,15 +234,19 @@ export class BffApiV1Service {
     );
   }
 
- postSelfServiceRegistrationsIdDocuments<TData = void>(id: string, options?: HttpClientBodyOptions): Observable<TData>;
- postSelfServiceRegistrationsIdDocuments<TData = void>(id: string, options?: HttpClientEventOptions): Observable<HttpEvent<TData>>;
- postSelfServiceRegistrationsIdDocuments<TData = void>(id: string, options?: HttpClientResponseOptions): Observable<AngularHttpResponse<TData>>;
+ postSelfServiceRegistrationsIdDocuments<TData = void>(id: string,
+    provideDocumentsRequest: ProvideDocumentsRequest, options?: HttpClientBodyOptions): Observable<TData>;
+ postSelfServiceRegistrationsIdDocuments<TData = void>(id: string,
+    provideDocumentsRequest: ProvideDocumentsRequest, options?: HttpClientEventOptions): Observable<HttpEvent<TData>>;
+ postSelfServiceRegistrationsIdDocuments<TData = void>(id: string,
+    provideDocumentsRequest: ProvideDocumentsRequest, options?: HttpClientResponseOptions): Observable<AngularHttpResponse<TData>>;
   postSelfServiceRegistrationsIdDocuments<TData = void>(
-    id: string, options?: HttpClientObserveOptions): Observable<TData | HttpEvent<TData> | AngularHttpResponse<TData>> {
+    id: string,
+    provideDocumentsRequest: ProvideDocumentsRequest, options?: HttpClientObserveOptions): Observable<TData | HttpEvent<TData> | AngularHttpResponse<TData>> {
     if (options?.observe === 'events') {
       return this.http.post<TData>(
       `/self-service/registrations/${id}/documents`,
-      undefined,{
+      provideDocumentsRequest,{
         ...(options as Omit<NonNullable<typeof options>, 'observe'>),
         observe: 'events',
       }
@@ -244,7 +256,7 @@ export class BffApiV1Service {
     if (options?.observe === 'response') {
       return this.http.post<TData>(
       `/self-service/registrations/${id}/documents`,
-      undefined,{
+      provideDocumentsRequest,{
         ...(options as Omit<NonNullable<typeof options>, 'observe'>),
         observe: 'response',
       }
@@ -253,7 +265,7 @@ export class BffApiV1Service {
 
     return this.http.post<TData>(
       `/self-service/registrations/${id}/documents`,
-      undefined,{
+      provideDocumentsRequest,{
         ...(options as Omit<NonNullable<typeof options>, 'observe'>),
         observe: 'body',
       }