fix: offer name in client detail, retainer forecast, LTV with offers, offers-sold chart

- Client detail offers: show offer macro name ("Mantenimento") instead of tier letter
- Forecast: retainers project the monthly fee across every month from start_date
  (no longer capped by duration_months); una_tantum unchanged
- Clients list LTV: per project max(accepted_total, sum of assigned offers) so a
  retainer with unset quote still counts
- Dashboard: new "Offerte vendute" chart (count by offer + tier)

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

src/components/admin/OffersSoldChart.tsx

@@ -0,0 +1,50 @@
+import type { OffersSoldBreakdown } from "@/lib/forecast-queries";
+
+export function OffersSoldChart({ data }: { data: OffersSoldBreakdown }) {
+  const max = Math.max(...data.rows.map((r) => r.count), 1);
+
+  if (data.rows.length === 0) {
+    return (
+      <div className="bg-white rounded-xl border border-[#e5e7eb] p-8 text-center">
+        <p className="text-sm text-[#71717a] italic">Nessuna offerta venduta finora.</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="bg-white rounded-xl border border-[#e5e7eb] p-6 space-y-4">
+      <div className="flex items-center justify-between">
+        <h3 className="text-sm font-bold text-[#1a1a1a]">Offerte vendute</h3>
+        <span className="inline-flex items-center justify-center min-w-[24px] h-6 px-2 rounded-full bg-[#1A463C] text-white text-xs font-bold">
+          {data.total}
+        </span>
+      </div>
+      <div className="space-y-3">
+        {data.rows.map((row, i) => {
+          const pct = Math.round((row.count / max) * 100);
+          return (
+            <div key={`${row.offer_name}-${row.tier_letter ?? "—"}-${i}`}>
+              <div className="flex items-center justify-between mb-1 gap-2">
+                <span className="text-sm font-medium text-[#1a1a1a] truncate">
+                  {row.offer_name}
+                  {row.tier_letter && (
+                    <span className="ml-2 inline-flex items-center rounded-full bg-[#1A463C]/10 px-2 py-0.5 text-[11px] font-semibold text-[#1A463C]">
+                      Tier {row.tier_letter}
+                    </span>
+                  )}
+                </span>
+                <span className="text-sm tabular-nums text-[#71717a] shrink-0">{row.count}</span>
+              </div>
+              <div className="h-2 rounded-full bg-[#f4f4f5] overflow-hidden">
+                <div
+                  className="h-full rounded-full bg-[#1A463C] transition-all"
+                  style={{ width: `${pct}%` }}
+                />
+              </div>
+            </div>
+          );
+        })}
+      </div>
+    </div>
+  );
+}