Show attachment download progress, new stop button to cancel

Co-authored-by: Jamie Kyle <jamie@signal.org>

ts/util/dropZero.ts

@@ -0,0 +1,11 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { isNumber } from 'lodash';
+
+export function dropZero(value: number | null | undefined): number | undefined {
+  if (isNumber(value) && value !== 0) {
+    return value;
+  }
+  return undefined;
+}