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/client/confirm.svelte.ts

@@ -4,6 +4,8 @@ export type ConfirmOptions = {
   confirmLabel?: string;
   cancelLabel?: string;
   destructive?: boolean;
+  /** If true, hide the cancel button — used for simple info/alert dialogs. */
+  infoOnly?: boolean;
 };
 
 type PendingRequest = ConfirmOptions & {
@@ -39,3 +41,14 @@ export function confirmAction(options: ConfirmOptions): Promise<boolean> {
   if (typeof window === 'undefined') return Promise.resolve(false);
   return confirmStore.ask(options);
 }
+
+/**
+ * Show a modal info dialog with a single OK button. Resolves when dismissed.
+ * Use instead of window.alert().
+ */
+export function alertAction(options: Omit<ConfirmOptions, 'destructive' | 'cancelLabel' | 'infoOnly'>): Promise<void> {
+  if (typeof window === 'undefined') return Promise.resolve();
+  return confirmStore
+    .ask({ ...options, infoOnly: true, confirmLabel: options.confirmLabel ?? 'OK' })
+    .then(() => undefined);
+}