feat(01-04): layout, routing, API hooks, tipi TypeScript, Dashboard, Settings

- types.ts: CalendarSlot, GeneratedPost, PostResult, JobStatus, Settings, SettingsStatus
- api/client.ts: aggiunto apiGet, apiPost, apiPut, apiDownload, triggerDownload
- api/hooks.ts: 10+ hooks TanStack Query (settings, generate, job polling, CSV export)
- components/Layout.tsx + Sidebar.tsx: sidebar stone/amber palette con 4 nav link
- pages/Dashboard.tsx: banner API key, quick actions link, step guide
- pages/Settings.tsx: form completo (API key password, LLM select, brand, nicchie checkbox)
- App.tsx: 5 route con BrowserRouter basename='/postgenerator', QueryClientProvider, Layout

frontend/src/components/Layout.tsx

@@ -0,0 +1,22 @@
+/**
+ * Layout wrapper principale con Sidebar a sinistra e area contenuto a destra.
+ * Tutti i child sono renderizzati nell'area contenuto scrollabile.
+ */
+
+import type { ReactNode } from 'react'
+import { Sidebar } from './Sidebar'
+
+interface LayoutProps {
+  children: ReactNode
+}
+
+export function Layout({ children }: LayoutProps) {
+  return (
+    <div className="flex min-h-screen bg-stone-900 text-stone-100">
+      <Sidebar />
+      <main className="flex-1 overflow-y-auto">
+        {children}
+      </main>
+    </div>
+  )
+}