feat: lead → client conversion + client contact fields (email/phone)

Blocco A+B (milestone v2.3). Migration 0011 is additive (ADD COLUMN only):
clients.email, clients.phone, leads.archived.

- createClientCore() extracted from createClient and reused by conversion
- clients.email/phone added to create + edit forms and shown on client header
  (never exposed on the public /client/[token] page)
- convertLeadToClient(): reuses core, carries over lead transcripts
  (client_transcripts.client_id), links project.created_from_lead_id,
  archives the lead while keeping its "won" status; idempotent
- "Converti in cliente" button on won leads; "Convertito → Apri cliente"
  once converted (clientId resolved via created_from_lead_id)
- archived leads hidden from list/kanban; detail page fetches by id incl. archived

Migration must be applied to the prod DB BEFORE this is deployed.

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

src/app/admin/leads/[id]/page.tsx

@@ -1,18 +1,21 @@
 import { notFound } from "next/navigation";
 import { getActivityLog, getUpcomingReminders, getTranscripts } from "@/lib/lead-service";
-import { getLeadsWithTags, getLeadFieldOptions } from "@/lib/admin-queries";
+import {
+  getLeadByIdWithTags,
+  getLeadFieldOptions,
+  getClientIdFromLead,
+} from "@/lib/admin-queries";
 import { LeadDetail } from "@/components/admin/leads/LeadDetail";
 
 export default async function LeadDetailPage({ params }: { params: Promise<{ id: string }> }) {
   const { id } = await params;
 
-  const [leads, options] = await Promise.all([
-    getLeadsWithTags(),
+  const [lead, options, convertedClientId] = await Promise.all([
+    getLeadByIdWithTags(id),
     getLeadFieldOptions(),
+    getClientIdFromLead(id),
   ]);
 
-  const lead = leads.find((l) => l.id === id);
-
   if (!lead) {
     notFound();
   }
@@ -31,6 +34,7 @@ export default async function LeadDetailPage({ params }: { params: Promise<{ id:
       tags={lead.tags}
       tagOptions={options.tags}
       transcripts={transcripts}
+      convertedClientId={convertedClientId}
     />
   );
 }