feat: implement AccessDeniedScreen and enhance error handling

- Introduced AccessDeniedScreen component for improved user experience when access is denied, replacing the previous AccessDenied component.
- Updated CurrentDutyView and CalendarPage to handle access denied scenarios, displaying the new screen appropriately.
- Enhanced tests for CurrentDutyView and AccessDeniedScreen to ensure correct rendering and functionality under access denied conditions.
- Refactored localization messages to include new labels for access denied scenarios in both English and Russian.

webapp-next/src/components/current-duty/CurrentDutyView.test.tsx

@@ -127,4 +127,25 @@ describe("CurrentDutyView", () => {
     expect(buttons[0]).toHaveAccessibleName(/Retry|Повторить/i);
     vi.mocked(fetchDuties).mockResolvedValue([]);
   });
+
+  it("403 shows AccessDeniedScreen with Back button and no Retry", async () => {
+    const { fetchDuties, AccessDeniedError } = await import("@/lib/api");
+    vi.mocked(fetchDuties).mockRejectedValue(
+      new AccessDeniedError("ACCESS_DENIED", "Custom 403 message")
+    );
+    const onBack = vi.fn();
+    render(<CurrentDutyView onBack={onBack} />);
+    await screen.findByText(/Access denied|Доступ запрещён/i, {}, { timeout: 3000 });
+    expect(
+      screen.getByText(/Open the app again from Telegram|Откройте приложение снова из Telegram/i)
+    ).toBeInTheDocument();
+    expect(screen.getByText("Custom 403 message")).toBeInTheDocument();
+    expect(
+      screen.getByRole("button", { name: /Back to calendar|Назад к календарю/i })
+    ).toBeInTheDocument();
+    expect(screen.queryByRole("button", { name: /Retry|Повторить/i })).not.toBeInTheDocument();
+    fireEvent.click(screen.getByRole("button", { name: /Back to calendar|Назад к календарю/i }));
+    expect(onBack).toHaveBeenCalled();
+    vi.mocked(fetchDuties).mockResolvedValue([]);
+  });
 });