Registratie: answer-driven required document uploads

Categories stay server-owned (ADR-0001); the FE sends its answers to
/uploads/categories and re-fetches reactively when they change:
- Diplomabewijs required only for a handmatig diploma (DUO is verified digitally;
  nothing required before a diploma is chosen).
- Bewijs Nederlandse taalvaardigheid required only when the applicant answers "ja"
  to the nl-taalvaardigheid (B2) policy question.
CategoriesFor(wizardId, diplomaHerkomst, taalvaardigheid) decides; Find uses the
maximal set so uploads still validate. CategoriesLoaded drops orphaned uploads
when a category disappears. Also: show the foreground-only upload banner only when
there is at least one category.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/shared/infrastructure/api-client.ts

@@ -448,14 +448,24 @@ export class ApiClient {
     }
 
     /**
+     * @param diplomaHerkomst (optional) 
+     * @param taalvaardigheid (optional) 
      * @return OK
      */
-    categories(wizardId: string): Promise<UploadCategoriesDto> {
+    categories(wizardId: string, diplomaHerkomst?: string | undefined, taalvaardigheid?: string | undefined): Promise<UploadCategoriesDto> {
         let url_ = this.baseUrl + "/api/v1/uploads/categories?";
         if (wizardId === undefined || wizardId === null)
             throw new globalThis.Error("The parameter 'wizardId' must be defined and cannot be null.");
         else
             url_ += "wizardId=" + encodeURIComponent("" + wizardId) + "&";
+        if (diplomaHerkomst === null)
+            throw new globalThis.Error("The parameter 'diplomaHerkomst' cannot be null.");
+        else if (diplomaHerkomst !== undefined)
+            url_ += "diplomaHerkomst=" + encodeURIComponent("" + diplomaHerkomst) + "&";
+        if (taalvaardigheid === null)
+            throw new globalThis.Error("The parameter 'taalvaardigheid' cannot be null.");
+        else if (taalvaardigheid !== undefined)
+            url_ += "taalvaardigheid=" + encodeURIComponent("" + taalvaardigheid) + "&";
         url_ = url_.replace(/[?&]$/, "");
 
         let options_: RequestInit = {