feat(frontend): restyle ThothII to the Omics Portal (GSD) design system

Adopt the portal's design language so the app embeds seamlessly into its
header/sidebar chrome later:
- Token layer rewritten as raw OKLCH triplets (the previous oklch()-wrapped
  vars produced invalid colors; the UI was effectively unstyled). Values mirror
  GSD: Manrope + Fraunces fonts, #cb333b red brand, warm off-white surfaces,
  pill buttons, brand focus rings. Dark tokens follow .dark or the portal's
  [data-bs-theme=dark].
- Layout: no left sidebar, no header (the portal supplies them). Conversation
  column flush-left with a slim F1-F8 phase strip; session rail moved to the
  RIGHT, mirroring the portal's left sidebar (red section label, red-tint active
  item). Editorial empty state.
- Transcript component now actually renders the streamed assistant turns (the
  store accumulated them but nothing displayed them). Toaster mounted for errors
  (matchMedia polyfill added to the jsdom test setup).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/test/setup.ts

@@ -1,6 +1,21 @@
 import "@testing-library/jest-dom/vitest";
 import { server } from "./msw";
 
+// jsdom lacks matchMedia; sonner's <Toaster> (mounted in AppShell) needs it.
+if (!window.matchMedia) {
+  window.matchMedia = (query: string) =>
+    ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addEventListener: () => {},
+      removeEventListener: () => {},
+      addListener: () => {},
+      removeListener: () => {},
+      dispatchEvent: () => false,
+    }) as unknown as MediaQueryList;
+}
+
 beforeAll(() => server.listen());
 afterEach(() => server.resetHandlers());
 afterAll(() => server.close());