feat(behandel): behandel-portal — werkbak + beoordeling (closes #13) (#87)

## What & why

Finishes **S-12 · Behandel-portal — werkbak + beoordeling**. The backend sub-slices (S-12a/b/c-1/c-2) were merged, but the slice's stated outcome — a behandel *portal* with medewerker login, a werkbak, and decide — had no frontend. This adds it.

- **`libs/auth`**: `MedewerkerAuthService` + `provideMedewerkerAuth` (Keycloak `medewerker` realm), a `roles`/`hasRole` surface on the shared `AuthService`, and a realm-roles protocol mapper so the SPA can read `behandelaar`/`teamlead` from the token. The BFF remains the security boundary (ADR-0013).
- **`apps/behandel`**: a new Nx Angular app mirroring self-service — medewerker OIDC login and a **werkbak** page listing registrations awaiting beoordeling (`GET /behandel/werkbak`) with per-row **Goedkeuren/Afwijzen** actions (`POST /behandel/registrations/{id}/decide`) that refresh the list. NL DS/Utrecht, standalone + signals.
- **e2e**: the walking-skeleton happy path now approves through the real portal (behandelaar logs in, finds the row by reference, clicks Goedkeuren) instead of the temporary admin endpoint.
- **infra/docs**: behandel service in compose (`:8142`, depends on Keycloak); added to the smoke `WAIT_SVCS` + CI log dump; `frontend-decisions.md` and `demo-script.md` updated.

Closes #13

## Definition of Done

- [x] Linked Gitea issue (above).
- [x] Failing test committed before the implementation.
- [x] Implementation makes the test pass; refactor commit if structure improved.
- [x] Conventional Commits referencing the issue (`refs #13`).
- [ ] CI green — all Gitea Actions jobs.
- [x] `docker compose up` from a fresh clone reaches green health checks within 3 minutes. *(behandel image + container verified locally; full stack gated in CI.)*
- [x] Docs updated if behaviour, contracts, or operations changed.
- [x] ADR added — ADR-0013 (merged with the backend sub-slices) already covers the wiring; no new decision here.
- [x] Demo note in `docs/demo-script.md`.

## Notes for reviewers

- Verified locally: auth + behandel + all frontend projects pass lint & unit tests (incl. axe WCAG 2.1 AA); production build green; the behandel Docker image builds and serves with the correct baked `medewerker` config + SPA fallback.
- The full compose-up smoke, e2e, and mutation are CI-gated (known local full-stack verify limits).
- **Follow-ups (not in scope):** the `WerkbakItem` contract has no citizen name (werkbak shows the BSN) — adding one is a BFF+domain contract change; and the domain's temporary admin `approve` endpoint is now unused by the e2e and could be removed.

Reviewed-on: #87

apps/behandel/src/app/werkbak/werkbak-page.html

@@ -0,0 +1,64 @@
+<main utrecht-document class="utrecht-theme">
+  <utrecht-article>
+    <utrecht-heading-1>Werkbak</utrecht-heading-1>
+    <p utrecht-paragraph>
+      Registraties die wachten op beoordeling. Keur elke registratie goed of wijs deze af.
+    </p>
+
+    @if (loading()) {
+      <p utrecht-paragraph role="status">Bezig met laden…</p>
+    } @else if (failed()) {
+      <p utrecht-paragraph role="alert">
+        Kon de werkbak niet laden. Controleer of je als behandelaar bent ingelogd en probeer het
+        opnieuw.
+      </p>
+    } @else if (loaded() && items().length === 0) {
+      <p utrecht-paragraph role="status">De werkbak is leeg.</p>
+    } @else if (items().length > 0) {
+      <table utrecht-table>
+        <caption>
+          Registraties in behandeling
+        </caption>
+        <thead>
+          <tr>
+            <th scope="col">Referentie</th>
+            <th scope="col">BSN</th>
+            <th scope="col">Status</th>
+            <th scope="col">Actie</th>
+          </tr>
+        </thead>
+        <tbody>
+          @for (item of items(); track item.registrationId) {
+            <tr>
+              <td>{{ item.registrationId }}</td>
+              <td>{{ item.bsn }}</td>
+              <td>{{ item.status }}</td>
+              <td>
+                <button
+                  utrecht-button
+                  appearance="primary-action-button"
+                  type="button"
+                  [attr.aria-label]="'Goedkeuren ' + item.registrationId"
+                  [disabled]="deciding() === item.registrationId"
+                  (click)="decide(item.registrationId, 'goedkeuren')"
+                >
+                  Goedkeuren
+                </button>
+                <button
+                  utrecht-button
+                  appearance="secondary-action-button"
+                  type="button"
+                  [attr.aria-label]="'Afwijzen ' + item.registrationId"
+                  [disabled]="deciding() === item.registrationId"
+                  (click)="decide(item.registrationId, 'afwijzen')"
+                >
+                  Afwijzen
+                </button>
+              </td>
+            </tr>
+          }
+        </tbody>
+      </table>
+    }
+  </utrecht-article>
+</main>