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/Dockerfile

@@ -0,0 +1,23 @@
+# Multi-stage build for the behandel portal (Angular → nginx).
+# Build context is the repo root (the app needs the pnpm workspace + libs). See infra/docker-compose.yml.
+FROM node:24-slim AS build
+WORKDIR /src
+RUN corepack enable && corepack prepare pnpm@11.5.2 --activate
+
+# Restore first (cached unless the manifests change).
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml nx.json tsconfig.base.json eslint.config.mjs ./
+RUN pnpm install --frozen-lockfile
+
+# Sources (only what the app + its libs need).
+COPY apps/behandel apps/behandel
+COPY libs libs
+RUN pnpm nx build behandel
+
+FROM nginx:1.27-alpine AS runtime
+COPY apps/behandel/nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /src/dist/apps/behandel/browser /usr/share/nginx/html
+# Compose-time OIDC config: the browser (Playwright, on the compose network) reaches Keycloak by
+# service name, so the token issuer matches the BFF's medewerker authority (host-consistent, ADR-0013).
+RUN printf '{ "authority": "http://keycloak:8080/realms/medewerker" }\n' > /usr/share/nginx/html/config.json
+
+EXPOSE 80