style: refine settings taxonomy UI (field cells, icon headers, 2-col grid)

- PoolManager: defined field cells with value count, refined chips,
  inline ghost + button, focus ring, pending/empty states
- TaxonomyManager: icon-badged section headers, ordered 2-col grid,
  sync explainer note
- Settings page: wider container (max-w-4xl) for the grid to breathe

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

src/app/admin/impostazioni/page.tsx

@@ -19,8 +19,8 @@ export default async function ImpostazioniPage() {
     <div>
       <h1 className="text-2xl font-bold text-[#1a1a1a] mb-6">Impostazioni</h1>
 
-      <div className="space-y-6 max-w-2xl">
-        <div className="bg-white rounded-xl border border-[#e5e7eb] p-6">
+      <div className="space-y-6 max-w-4xl">
+        <div className="bg-white rounded-xl border border-[#e5e7eb] p-6 max-w-md">
           <h2 className="text-base font-semibold text-[#1a1a1a] mb-4">Analytics Profittabilità</h2>
 
           <form action={handleSave} className="space-y-4">