Unmount Dialog children when closed

The native <dialog> wrapper rendered its children unconditionally
and only called dialog.close() on the underlying element when
open went false. The React subtree stayed mounted, so component
state (e.g. a ConfirmButton mid-confirm with a red checkmark
showing) survived a close/reopen cycle and reappeared the next
time the user opened the same dialog.

Gate children on open so the subtree unmounts on close. Next open
gets a fresh tree with default state.

apps/web/src/components/ui/dialog.tsx

@@ -46,7 +46,7 @@ export function Dialog({ open, onClose, className, children }: DialogProps) {
 				className,
 			)}
 		>
-			<div className="p-6">{children}</div>
+			{open ? <div className="p-6">{children}</div> : null}
 		</dialog>
 	);
 }