feat: pagina Conversazioni — inbox unificata messaggi clienti

Nuova pagina admin /admin/conversazioni: vista WhatsApp-style (lista
conversazioni a sinistra, thread + risposta a destra) che aggrega i
messaggi di tutti i clienti dalla tabella comments, cross-cliente.

- Migration additiva 0014: clients.admin_last_read_at per tracciare
  letto/non-letto (pallini + badge in sidebar). Applicata a prod.
- conversations-queries.ts: aggregazione entity_id → cliente
  (general/phase/task/deliverable), getConversations /
  getConversationThread / getUnreadConversationsCount.
- Risposte admin salvate come commento "general" (visibili anche nella
  chat cliente e nel CommentsTab della scheda).
- Voce di menu + badge non-letti (AdminSidebar/AdminShell/layout).
- Token semantici per dual light/dark; refresh manuale (no polling).

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

src/app/admin/conversazioni/page.tsx

@@ -0,0 +1,41 @@
+import { PageHeader } from "@/components/admin/PageHeader";
+import { ConversationsView } from "@/components/admin/conversazioni/ConversationsView";
+import {
+  getConversations,
+  getConversationThread,
+} from "@/lib/conversations-queries";
+
+export const revalidate = 0;
+
+export default async function ConversazioniPage({
+  searchParams,
+}: {
+  searchParams: Promise<{ c?: string }>;
+}) {
+  const { c } = await searchParams;
+
+  const conversations = await getConversations();
+  // Default selection: the requested client, else the most recent conversation.
+  const activeClientId =
+    (c && conversations.some((conv) => conv.clientId === c) ? c : null) ??
+    conversations[0]?.clientId ??
+    null;
+
+  const activeThread = activeClientId
+    ? await getConversationThread(activeClientId)
+    : null;
+
+  return (
+    <div className="space-y-6">
+      <PageHeader
+        title="Conversazioni"
+        subtitle="Centro messaggi clienti — tutte le richieste in un unico posto"
+      />
+      <ConversationsView
+        conversations={conversations}
+        activeThread={activeThread}
+        activeClientId={activeClientId}
+      />
+    </div>
+  );
+}