fix(notifications): a notice's button is said when shown, like its text

An action label was translated when the notice was raised, so after a language switch a live
toast or center row read in one language with its button in the other. The access-requests nudge
no longer re-issues on a switch for it. New tests: the button and a server refusal follow a
switch.

frontend/src/components/ui/Toaster.language.dom.test.tsx

@@ -32,6 +32,37 @@ describe("a notice speaks the reader's language of the moment", () => {
     expect(screen.queryByText(en)).toBeNull();
   });
 
+  it("its button is said again too, beside the text it acts on", async () => {
+    render(<Toaster />);
+    act(
+      () =>
+        void notify({
+          message: msg("common.copy.done"),
+          action: { label: msg("common.undo"), onClick: () => {} },
+        }),
+    );
+    expect(screen.getByRole("button", { name: "Undo" })).toBeTruthy();
+
+    await act(async () => void (await i18n.changeLanguage("hu")));
+    expect(screen.getByRole("button", { name: "Visszavonás" })).toBeTruthy();
+    expect(screen.queryByRole("button", { name: "Undo" })).toBeNull();
+  });
+
+  it("a server refusal is said again in the language of the moment", async () => {
+    render(<Toaster />);
+    act(
+      () =>
+        void notify({
+          level: "error",
+          message: { detail: { code: "not_found", reason: "view" } },
+        }),
+    );
+    expect(screen.getByText("This view doesn't exist any more")).toBeTruthy();
+
+    await act(async () => void (await i18n.changeLanguage("hu")));
+    expect(screen.getByText("Ez a nézet már nem létezik")).toBeTruthy();
+  });
+
   it("a value inside the text is said again too, and a number is grouped the reader's way", async () => {
     const text = msg("settings.takeout.read", {
       name: raw("watch-history.json"),