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/lib/client/confirm.svelte.ts

@@ -0,0 +1,41 @@
+export type ConfirmOptions = {
+  title: string;
+  message?: string;
+  confirmLabel?: string;
+  cancelLabel?: string;
+  destructive?: boolean;
+};
+
+type PendingRequest = ConfirmOptions & {
+  resolve: (result: boolean) => void;
+};
+
+class ConfirmStore {
+  pending = $state<PendingRequest | null>(null);
+
+  ask(options: ConfirmOptions): Promise<boolean> {
+    // If another dialog is already open, close it as cancelled so we don't stack.
+    if (this.pending) this.pending.resolve(false);
+    return new Promise<boolean>((resolve) => {
+      this.pending = { ...options, resolve };
+    });
+  }
+
+  answer(result: boolean): void {
+    if (!this.pending) return;
+    const p = this.pending;
+    this.pending = null;
+    p.resolve(result);
+  }
+}
+
+export const confirmStore = new ConfirmStore();
+
+/**
+ * Show a modal confirmation dialog. Resolves to true on confirm, false on cancel/Escape.
+ * Safe on the server: falls back to the native confirm() only in the browser.
+ */
+export function confirmAction(options: ConfirmOptions): Promise<boolean> {
+  if (typeof window === 'undefined') return Promise.resolve(false);
+  return confirmStore.ask(options);
+}