feat: init payments + split payment in project workspace

- initProjectPayments: crea Acconto 50%/Saldo 50% se il progetto non ha pagamenti
- splitPayment: divide un pagamento in due rate con importi custom
- SplitPaymentForm: form client interattivo con anteprima live della rata 2
- PaymentsTab: stato vuoto con CTA + pulsante Dividi per ogni riga
- projectId prop opzionale per attivare le feature solo nel contesto progetto

src/components/admin/tabs/PaymentsTab.tsx

@@ -2,15 +2,18 @@ import {
   updatePaymentStatus,
   updateAcceptedTotal,
 } from "@/app/admin/clients/[id]/actions";
+import { initProjectPayments } from "@/app/admin/projects/project-actions";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
+import { SplitPaymentForm } from "@/components/admin/SplitPaymentForm";
 import type { Payment } from "@/db/schema";
 
 type Props = {
   payments: Payment[];
   acceptedTotal: string;
   clientId: string;
+  projectId?: string; // set only from project detail page — enables init & split
 };
 
 const statusLabels: Record<string, string> = {
@@ -19,7 +22,7 @@ const statusLabels: Record<string, string> = {
   saldato: "Saldato",
 };
 
-export async function PaymentsTab({ payments, acceptedTotal, clientId }: Props) {
+export async function PaymentsTab({ payments, acceptedTotal, clientId, projectId }: Props) {
   return (
     <div className="space-y-6 max-w-md">
       {/* Accepted total */}
@@ -53,45 +56,76 @@ export async function PaymentsTab({ payments, acceptedTotal, clientId }: Props)
         </p>
       </div>
 
-      {/* Payment rows */}
-      {payments.map((p) => (
-        <div
-          key={p.id}
-          className="bg-white border border-gray-200 rounded-lg p-4"
-        >
-          <div className="flex items-center justify-between mb-2">
-            <h3 className="font-medium text-gray-900">{p.label}</h3>
-            <span className="text-sm text-gray-600">
-              €{" "}
-              {parseFloat(p.amount).toLocaleString("it-IT", {
-                minimumFractionDigits: 2,
-              })}
-            </span>
-          </div>
+      {/* Empty state — project has no payments yet */}
+      {projectId && payments.length === 0 && (
+        <div className="bg-white border border-dashed border-gray-300 rounded-lg p-6 text-center">
+          <p className="text-sm text-[#71717a] mb-4">
+            Nessun pagamento configurato. Crea le rate standard Acconto e Saldo.
+          </p>
           <form
-            action={async (fd: FormData) => {
+            action={async () => {
               "use server";
-              await updatePaymentStatus(p.id, clientId, fd.get("status") as string);
+              await initProjectPayments(projectId);
             }}
-            className="flex items-center gap-2"
           >
-            <select
-              name="status"
-              defaultValue={p.status}
-              className="text-sm border border-gray-200 rounded px-2 py-1.5 bg-white flex-1"
-            >
-              {Object.entries(statusLabels).map(([val, label]) => (
-                <option key={val} value={val}>
-                  {label}
-                </option>
-              ))}
-            </select>
-            <Button type="submit" size="sm" variant="outline">
-              Aggiorna
+            <Button type="submit" size="sm">
+              Crea Acconto &amp; Saldo
             </Button>
           </form>
         </div>
-      ))}
+      )}
+
+      {/* Payment rows */}
+      {payments.map((p) => {
+        const amount = parseFloat(p.amount);
+        return (
+          <div
+            key={p.id}
+            className="bg-white border border-gray-200 rounded-lg p-4"
+          >
+            <div className="flex items-center justify-between mb-2">
+              <h3 className="font-medium text-gray-900">{p.label}</h3>
+              <div className="flex items-center gap-2">
+                <span className="text-sm text-gray-600">
+                  €{" "}
+                  {amount.toLocaleString("it-IT", {
+                    minimumFractionDigits: 2,
+                  })}
+                </span>
+                {projectId && amount > 0 && (
+                  <SplitPaymentForm
+                    paymentId={p.id}
+                    projectId={projectId}
+                    currentAmount={amount}
+                  />
+                )}
+              </div>
+            </div>
+            <form
+              action={async (fd: FormData) => {
+                "use server";
+                await updatePaymentStatus(p.id, clientId, fd.get("status") as string);
+              }}
+              className="flex items-center gap-2"
+            >
+              <select
+                name="status"
+                defaultValue={p.status}
+                className="text-sm border border-gray-200 rounded px-2 py-1.5 bg-white flex-1"
+              >
+                {Object.entries(statusLabels).map(([val, label]) => (
+                  <option key={val} value={val}>
+                    {label}
+                  </option>
+                ))}
+              </select>
+              <Button type="submit" size="sm" variant="outline">
+                Aggiorna
+              </Button>
+            </form>
+          </div>
+        );
+      })}
     </div>
   );
 }