refactor: add successOr, sweep remaining inline unwraps (RD-17)

Eight sites hand-rolled `rd.tag === 'Success' ? rd.value : fallback`. Six
take the new `successOr(rd, fallback)`, one takes the existing `successOf`,
and one (`big-profile.store.ts`) uses the existing `map`, since it returns a
RemoteData rather than an unwrapped value.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/ssp/src/app/registratie/ui/registratie-wizard/registratie-wizard.component.ts

@@ -21,7 +21,7 @@ import { ASYNC } from '@shared/ui/async/async.component';
 import { AddressFieldsComponent } from '@registratie/ui/address-fields/address-fields.component';
 import { createStore } from '@shared/application/store';
 import { whenTag } from '@shared/kernel/fp';
-import { RemoteData } from '@shared/application/remote-data';
+import { RemoteData, successOr } from '@shared/application/remote-data';
 import { RegistratieLookupStore } from '@registratie/application/registratie-lookup.store';
 import { DuoLookupDto, PolicyQuestionDto } from '@registratie/contracts/duo-diplomas.dto';
 import {
@@ -516,10 +516,7 @@ export class RegistratieWizardComponent {
       inside it too: `<ng-template appAsyncLoaded>`'s own context can't inherit a
       generic from the sibling [data] input (Angular only infers a structural
       directive's type parameter from an input on that same node). */
-  protected duoData = computed<DuoLookupDto | null>(() => {
-    const rd = this.lookupRd();
-    return rd.tag === 'Success' ? rd.value : null;
-  });
+  protected duoData = computed<DuoLookupDto | null>(() => successOr(this.lookupRd(), null));
 
   readonly jaNee = JA_NEE;