feat(ui): custom dialog replaces all remaining window.alert() calls

alertAction({title, message}) returns Promise<void> and renders the
same ConfirmDialog with infoOnly:true — single OK button, no Abbrechen.
Replaces:
- 'Bitte Profil wählen.' (recipe rating / favorite / cooked / comment)
- 'Bitte Profil wählen, um zu liken.' (wishlist)
- 'Profil konnte nicht angelegt werden' (ProfileSwitcher)
- 'Umbenennen fehlgeschlagen' (admin/profiles)
- 'Speichern fehlgeschlagen' (preview)

No window.alert() or window.confirm() left in the codebase.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -1,6 +1,6 @@
 <script lang="ts">
   import { profileStore } from '$lib/client/profile.svelte';
-  import { confirmAction } from '$lib/client/confirm.svelte';
+  import { confirmAction, alertAction } from '$lib/client/confirm.svelte';
 
   let newName = $state('');
   let newEmoji = $state('🍳');
@@ -31,7 +31,10 @@
     });
     if (!res.ok) {
       const body = await res.json().catch(() => ({}));
-      alert(`Fehler: ${body.message ?? res.status}`);
+      await alertAction({
+        title: 'Umbenennen fehlgeschlagen',
+        message: body.message ?? `HTTP ${res.status}`
+      });
       return;
     }
     await profileStore.load();