fix(ui): a reviewed log takes the focus back once, and a dialog's focus survives a Retry

E32 review round 1 (F1, F2).

- Issue composer: the review's focus-return token became state in S4 and was never spent, so every
  Preview → Edit round trip remounted the attachments and moved the focus from the toggle to the
  log's Review button. The token is cleared once it has been used, as the ref was.
- Modal (initialFocus "field"): the late-form watch moved the focus to the first control once and
  stopped. A failed load's Retry then gave way to the spinner, its focus fell to <body> inside the
  aria-modal dialog, and the form's first field never got it. The watch now re-arms when the focus
  falls to <body>: it waits on the ✕ and moves to the first field when the form arrives. Focus in a
  dialog stacked on top is left alone.

frontend/src/components/downloadAdmin.dom.test.tsx

@@ -53,6 +53,21 @@ describe("the download-quota editor", () => {
     expect(get).toHaveBeenCalledTimes(2);
   });
 
+  it("gives the first field the focus when the form arrives after a retry", async () => {
+    // jsdom lays nothing out, so every element reads as hidden to the dialog's focus rules.
+    vi.spyOn(HTMLElement.prototype, "offsetParent", "get").mockReturnValue(document.body);
+    vi.spyOn(api, "adminGetDownloadQuota")
+      .mockRejectedValueOnce(new Error("down"))
+      .mockResolvedValueOnce(QUOTA as never);
+    open();
+    await screen.findByRole("alert");
+    const retry = screen.getByText("common.retry").closest("button")!;
+    await waitFor(() => expect(document.activeElement).toBe(retry));
+    fireEvent.click(retry); // the Retry gives way to the spinner: its focus must not fall to <body>
+    const first = await screen.findByDisplayValue("5");
+    await waitFor(() => expect(document.activeElement).toBe(first));
+  });
+
   it("saves the GB field as bytes, and the reset drops the override", async () => {
     vi.spyOn(api, "adminGetDownloadQuota").mockResolvedValue(QUOTA as never);
     const set = vi.spyOn(api, "adminSetDownloadQuota").mockResolvedValue(QUOTA as never);