feat(ui): custom confirmation dialog replacing native window.confirm

Single reusable dialog with a promise-based API: confirmAction({...})
returns Promise<boolean>. Supports title, optional message body,
confirm/cancel labels, and a 'destructive' flag that paints the confirm
button red.

Accessibility: Escape cancels, Enter confirms, confirm button auto-focus,
role=dialog + aria-labelledby, backdrop click = cancel.

Rolled out to: recipe delete, domain remove, profile delete, wishlist
remove. Native confirm() is gone from the codebase.

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

src/routes/+layout.svelte

@@ -2,6 +2,7 @@
   import { onMount } from 'svelte';
   import { profileStore } from '$lib/client/profile.svelte';
   import ProfileSwitcher from '$lib/components/ProfileSwitcher.svelte';
+  import ConfirmDialog from '$lib/components/ConfirmDialog.svelte';
 
   let { children } = $props();
 
@@ -10,6 +11,8 @@
   });
 </script>
 
+<ConfirmDialog />
+
 <header class="bar">
   <a href="/" class="brand">Kochwas</a>
   <div class="bar-right">