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

libs/auth/src/lib/medewerker-auth.providers.ts

@@ -0,0 +1,49 @@
+import { EnvironmentProviders, makeEnvironmentProviders } from '@angular/core';
+import { LogLevel, provideAuth, withAppInitializerAuthCheck } from 'angular-auth-oidc-client';
+import { AuthService } from './auth.service';
+import { MedewerkerAuthService } from './medewerker-auth.service';
+
+export interface MedewerkerAuthOptions {
+  /** The Keycloak `medewerker` realm issuer, as reachable from the browser. */
+  authority: string;
+  /** Where Keycloak redirects back to after login (usually the app origin). */
+  redirectUrl: string;
+  /**
+   * Route prefixes whose requests get the bearer token attached. The api-client calls the BFF with
+   * **relative** URLs (same-origin via the nginx proxy), so these must be relative path prefixes
+   * (e.g. `/behandel/`) — angular-auth-oidc-client matches `req.url.startsWith(route)`, and a
+   * relative `req.url` never starts with an absolute origin.
+   */
+  secureRoutes: string[];
+}
+
+/**
+ * Configure medewerker login (Keycloak `medewerker` realm, public client `big-portal`, auth-code +
+ * PKCE) and bind {@link AuthService} to the medewerker-backed implementation. Register
+ * {@link authInterceptor} (re-exported from digid-auth.providers) in the app's HttpClient so BFF
+ * calls carry the token.
+ */
+export function provideMedewerkerAuth(options: MedewerkerAuthOptions): EnvironmentProviders {
+  return makeEnvironmentProviders([
+    provideAuth(
+      {
+        config: {
+          authority: options.authority,
+          redirectUrl: options.redirectUrl,
+          postLogoutRedirectUri: options.redirectUrl,
+          clientId: 'big-portal',
+          scope: 'openid profile',
+          responseType: 'code',
+          silentRenew: true,
+          useRefreshToken: true,
+          secureRoutes: options.secureRoutes,
+          logLevel: LogLevel.Warn,
+        },
+      },
+      // Run checkAuth() at startup so the login callback (?code=…) is processed before the router
+      // and guard run — without it the guard sees "not authenticated" and re-triggers login (loop).
+      withAppInitializerAuthCheck(),
+    ),
+    { provide: AuthService, useClass: MedewerkerAuthService },
+  ]);
+}