feat(fp): WP-06 — kill $any() in templates (18x)

Make AsyncLoadedDirective generic with a static ngTemplateContextGuard for
AsyncComponent's own internal typing. That can't propagate to consumer
`<ng-template appAsyncLoaded let-p>` sites though -- Angular only infers a
structural directive's type parameter from an input bound on that same
node, not from a sibling input on the parent component -- so the ~9
root-cause consumers (dashboard, registration-detail, aanvraag-detail,
registratie-wizard) instead unwrap the RemoteData Success value via a
typed computed() and narrow it locally with `@if (x(); as p)`. The
remaining union-narrowing casts (registration-summary, showcase concepts
page) are replaced with a stable @let binding and a direct resource read,
respectively. Documented as a deviation in WP-06's backlog file.

src/app/showcase/concepts.page.ts

@@ -223,9 +223,9 @@ function fakeResource<T>(status: string, value?: T, error?: Error): Resource<T>
             >
             <p class="tag plain">Success</p>
             <app-async [resource]="successRes" [isEmpty]="isEmpty"
-              ><ng-template appAsyncLoaded let-v
+              ><ng-template appAsyncLoaded
                 ><ul>
-                  @for (i of v; track i) {
+                  @for (i of successRes.value(); track i) {
                     <li>{{ i }}</li>
                   }
                 </ul></ng-template
@@ -258,16 +258,17 @@ function fakeResource<T>(status: string, value?: T, error?: Error): Resource<T>
               placeholder="Typ een postcode, bijv. 1234 AB"
             />
           </div>
-          <div class="card" [class.card--good]="parsed().ok" [class.card--bad]="!parsed().ok">
-            @if (parsed().ok) {
+          @let r = parsed();
+          <div class="card" [class.card--good]="r.ok" [class.card--bad]="!r.ok">
+            @if (r.ok) {
               <p class="tag good">ok</p>
-              <pre>Postcode ="{{ $any(parsed()).value }}"</pre>
+              <pre>Postcode ="{{ r.value }}"</pre>
               <p class="note">
                 Een gevalideerde <code>Postcode</code> is een ander type dan een ruwe string.
               </p>
             } @else {
               <p class="tag bad">err</p>
-              <pre>{{ $any(parsed()).error }}</pre>
+              <pre>{{ r.error }}</pre>
             }
           </div>
         </div>