Prompt the user when key storage is unexpectedly off (#29912)

* Assert that we set backup_disabled when turning off key storage

* Prompt the user when key storage is unexpectedly off

* Playwright tests for the Turn on key storage toast

test/unit-tests/components/views/dialogs/ConfirmKeyStorageOffDialog-test.tsx

@@ -0,0 +1,40 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import React from "react";
+import { render } from "jest-matrix-react";
+
+import ConfirmKeyStorageOffDialog from "../../../../../src/components/views/dialogs/ConfirmKeyStorageOffDialog";
+
+describe("ConfirmKeyStorageOffDialog", () => {
+    beforeEach(() => {
+        jest.resetAllMocks();
+    });
+
+    it("renders", () => {
+        const dialog = render(<ConfirmKeyStorageOffDialog onFinished={jest.fn()} />);
+        expect(dialog.asFragment()).toMatchSnapshot();
+    });
+
+    it("calls onFinished with dismissed=true if we dismiss", () => {
+        const onFinished = jest.fn();
+        const dialog = render(<ConfirmKeyStorageOffDialog onFinished={onFinished} />);
+
+        dialog.getByRole("button", { name: "Yes, dismiss" }).click();
+
+        expect(onFinished).toHaveBeenCalledWith(true);
+    });
+
+    it("calls onFinished with dismissed=true if we continue", () => {
+        const onFinished = jest.fn();
+        const dialog = render(<ConfirmKeyStorageOffDialog onFinished={onFinished} />);
+
+        dialog.getByRole("button", { name: "Go to Settings" }).click();
+
+        expect(onFinished).toHaveBeenCalledWith(false);
+    });
+});