Add full shell, replaceable Omics adapter and bilingual interaction

Implement approved specification #32 and tickets #33-#37. Keep host authentication server-verified and pin session interaction language. Compile scoped base selectors for browser compatibility and retain full gutters during CSS pruning.

frontend/src/components/ErrorBoundary.test.tsx

@@ -1,4 +1,5 @@
-import { render, screen } from "@testing-library/react";
+import { act, render, screen } from "@testing-library/react";
+import { setLocale } from "../i18n";
 import userEvent from "@testing-library/user-event";
 import { useState } from "react";
 import { ErrorBoundary } from "./ErrorBoundary";
@@ -16,9 +17,18 @@ beforeEach(() => {
   errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
 });
 afterEach(() => {
+  act(() => setLocale("en"));
   errorSpy.mockRestore();
 });
 
+test("updates an already displayed error boundary when the locale changes", () => {
+  render(<ErrorBoundary label="document"><Boom boom label="SELECT * malformed" /></ErrorBoundary>);
+  act(() => setLocale("it"));
+  expect(screen.getByRole("alert")).toHaveTextContent("Impossibile visualizzare questo elemento (documento).");
+  expect(screen.getByRole("button", { name: "Riprova" })).toBeVisible();
+  expect(screen.getByText("SELECT * malformed")).toBeInTheDocument();
+});
+
 test("renders children when nothing throws", () => {
   render(
     <ErrorBoundary>