fix(files): an upload is said once in any order, copy buttons speak, a link list that failed says so

- The queue holds an upload it sees land done while this tab's upload still waits for its answer, so
  the dialog's notice is the only one whichever comes first; another device's upload follows after.
- One `useCopyFeedback` for every Copy beside a value (token, share link, set-password link): Copied
  for a moment, a notice a screen reader hears, a warning when the clipboard refuses; the token
  dialog's two Copy buttons are named by what they copy.
- The share dialog's link list shows loading, and a load error with Retry, never "no links" — and no
  New link beside a list it has not seen.
- The settings texts say that signing out elsewhere or a password change revokes the API tokens.
- DESIGN.md logs the folder-link decisions; the design lab keeps only the chosen renderings of the
  Links, Tokens and Files rounds.

frontend/src/components/useCopyFeedback.dom.test.ts

@@ -0,0 +1,42 @@
+// @vitest-environment jsdom
+//
+// A Copy button beside its value: "Copied" for a moment and a notice a screen reader hears, or a
+// warning when the clipboard refused — the same at every such button.
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { act, renderHook } from "@testing-library/react";
+
+const h = vi.hoisted(() => ({ copyText: vi.fn(async (_t: string) => true), notify: vi.fn() }));
+vi.mock("react-i18next", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("react-i18next")>()),
+  useTranslation: () => ({ i18n: { language: "en" }, t: (key: string) => key }),
+}));
+vi.mock("../lib/clipboard", () => ({ copyText: h.copyText }));
+vi.mock("../lib/notifications", () => ({ notify: h.notify }));
+
+import { useCopyFeedback } from "./useCopyFeedback";
+
+afterEach(() => {
+  vi.useRealTimers();
+  h.notify.mockClear();
+});
+
+describe("useCopyFeedback", () => {
+  it("a copy that worked reads Copied for a moment and is said out loud", async () => {
+    vi.useFakeTimers();
+    const { result } = renderHook(() => useCopyFeedback());
+    await act(() => result.current.copy("sfl_x"));
+    expect(h.copyText).toHaveBeenCalledWith("sfl_x");
+    expect(result.current.copied).toBe(true);
+    expect(h.notify).toHaveBeenCalledWith({ level: "success", message: "common.copy.done" });
+    act(() => void vi.advanceTimersByTime(2000));
+    expect(result.current.copied).toBe(false);
+  });
+
+  it("a copy the clipboard refused is a warning, and nothing reads Copied", async () => {
+    h.copyText.mockResolvedValueOnce(false);
+    const { result } = renderHook(() => useCopyFeedback());
+    await act(() => result.current.copy("sfl_x"));
+    expect(result.current.copied).toBe(false);
+    expect(h.notify).toHaveBeenCalledWith({ level: "warning", message: "common.copy.failed" });
+  });
+});