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/shell/NewSessionDialog.tsx

@@ -55,7 +55,7 @@ export function NewSessionDialog({ onCreated }: Props) {
         </DialogHeader>
         <form onSubmit={handleSubmit} className="flex flex-col gap-3">
           <div>
-            <label className="block text-xs font-medium mb-1" htmlFor="nsd-question">
+            <label className="mb-1.5 block text-xs font-medium text-muted-foreground" htmlFor="nsd-question">
               Domanda
             </label>
             <textarea
@@ -63,7 +63,7 @@ export function NewSessionDialog({ onCreated }: Props) {
               value={question}
               onChange={(e) => setQuestion(e.target.value)}
               rows={3}
-              className="w-full border rounded px-2 py-1 text-sm focus:outline-none focus:ring-1 resize-none"
+              className="w-full resize-none rounded-lg border border-input bg-card px-3 py-2 text-sm outline-none transition-colors placeholder:text-muted-foreground focus:border-primary/50 focus:ring-3 focus:ring-ring/15"
               placeholder="Inserisci la tua domanda…"
             />
           </div>