refactor: split dashboard.page.ts into per-concern sections

Each dashboard section (Mijn aanvragen, Wat moet ik regelen, Mijn
registratie, Specialismen, Wat wilt u doen, Beheer) now owns its own
store access, async state, and template. DashboardPage becomes pure
composition.

Extract the repeated RemoteData Success-narrowing pattern into
successOf() and the dashboard sort/split logic into
sortForDashboard/concepten/ingediend, both with tests.

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

apps/ssp/src/app/registratie/ui/registration-detail.page.ts

@@ -1,4 +1,5 @@
 import { Component, computed, inject } from '@angular/core';
+import { successOf } from '@shared/application/remote-data';
 import { PageShellComponent } from '@shared/layout/page-shell/page-shell.component';
 import { SkeletonComponent } from '@shared/ui/skeleton/skeleton.component';
 import { ASYNC } from '@shared/ui/async/async.component';
@@ -41,9 +42,7 @@ import { BigProfileStore } from '@registratie/application/big-profile.store';
 export class RegistrationDetailPage {
   protected store = inject(BigProfileStore);
 
-  /** See DashboardPage's `profile` for why this narrows via a computed instead of `let-`. */
-  protected readonly profile = computed(() => {
-    const rd = this.store.profile();
-    return rd.tag === 'Success' ? rd.value : undefined;
-  });
+  /** `successOf`: `<ng-template>` can't inherit a generic from a sibling host input,
+      so the Success value is unwrapped here instead of through `let-`. */
+  protected readonly profile = computed(() => successOf(this.store.profile()));
 }