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/lib/components/ProfileSwitcher.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
   import { profileStore } from '$lib/client/profile.svelte';
+  import { alertAction } from '$lib/client/confirm.svelte';
 
   let showModal = $state(false);
   let newName = $state('');
@@ -13,7 +14,10 @@
       newName = '';
       showModal = false;
     } catch (e) {
-      alert((e as Error).message);
+      await alertAction({
+        title: 'Profil konnte nicht angelegt werden',
+        message: (e as Error).message
+      });
     }
   }
 </script>