feat(frontend): add Settings menu item under Nuova domanda

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

frontend/src/shell/AppShell.tsx

@@ -3,6 +3,7 @@ import { useSessionStream } from "../stream/useSessionStream";
 import { WidgetHost } from "./WidgetHost";
 import { NavSessions } from "./NavSessions";
 import { NewSessionDialog } from "./NewSessionDialog";
+import { SettingsDialog } from "./SettingsDialog";
 import { SteerInput } from "./SteerInput";
 import { WorkflowBar } from "./WorkflowBar";
 
@@ -25,6 +26,7 @@ export function AppShell() {
       {/* Left nav: new session button + sessions list */}
       <aside className="w-48 border-r p-2 flex flex-col gap-2">
         <NewSessionDialog onCreated={handleCreated} />
+        <SettingsDialog />
         <NavSessions
           activeSessionId={activeSessionId}
           onSessionSelect={handleSessionSelect}