refactor(client): requireProfile() + asyncFetch wrapper

requireProfile():
- src/lib/client/profile.svelte.ts: neuer Helper, returnt das aktive
  Profile oder null nach standardisiertem alertAction
- 5x in recipes/[id]/+page.svelte: setRating, toggleFavorite, logCooked,
  addComment, toggleWishlist verlieren je 7 Zeilen Guard-Klausel
- profile-Variable im Closure macht den ! am profileStore.active obsolet

asyncFetch():
- src/lib/client/api-fetch-wrapper.ts: returnt Response auf 2xx, null
  nach alertAction auf Fehler
- 4 Call-Sites umgestellt: saveRecipe + saveTitle (recipes/[id]),
  saveEdit (admin/domains), rename (admin/profiles)
- admin/domains add() bewusst nicht migriert — inline-Error-UX statt Modal

Findings aus REVIEW-2026-04-18.md (Quick-Win 5) und redundancy.md

src/routes/admin/profiles/+page.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
   import { profileStore } from '$lib/client/profile.svelte';
-  import { confirmAction, alertAction } from '$lib/client/confirm.svelte';
+  import { confirmAction } from '$lib/client/confirm.svelte';
+  import { asyncFetch } from '$lib/client/api-fetch-wrapper';
   import { requireOnline } from '$lib/client/require-online';
 
   let newName = $state('');
@@ -27,19 +28,16 @@
     const next = prompt('Neuer Name:', currentName);
     if (!next || next === currentName) return;
     if (!requireOnline('Das Umbenennen')) return;
-    const res = await fetch(`/api/profiles/${id}`, {
-      method: 'PATCH',
-      headers: { 'content-type': 'application/json' },
-      body: JSON.stringify({ name: next.trim() })
-    });
-    if (!res.ok) {
-      const body = await res.json().catch(() => ({}));
-      await alertAction({
-        title: 'Umbenennen fehlgeschlagen',
-        message: body.message ?? `HTTP ${res.status}`
-      });
-      return;
-    }
+    const res = await asyncFetch(
+      `/api/profiles/${id}`,
+      {
+        method: 'PATCH',
+        headers: { 'content-type': 'application/json' },
+        body: JSON.stringify({ name: next.trim() })
+      },
+      'Umbenennen fehlgeschlagen'
+    );
+    if (!res) return;
     await profileStore.load();
   }