feat(portal-frontend): add worklist and case-detail typed interfaces and API services

Types mirror New.Api.Contracts verbatim; all write calls use the href
given in a case's actions block rather than a client-built URL.

portal-frontend/src/app/app.config.ts

@@ -1,4 +1,5 @@
 import { ApplicationConfig, provideBrowserGlobalErrorListeners } from '@angular/core';
+import { provideHttpClient } from '@angular/common/http';
 import { provideRouter } from '@angular/router';
 
 import { routes } from './app.routes';
@@ -6,6 +7,7 @@ import { routes } from './app.routes';
 export const appConfig: ApplicationConfig = {
   providers: [
     provideBrowserGlobalErrorListeners(),
-    provideRouter(routes)
+    provideRouter(routes),
+    provideHttpClient()
   ]
 };