Add balance transactions to user admin panel

Introduces BalanceTransaction model to track per-user balance history
(prepayments, refunds, partner credits). Admin can add/delete transactions;
current balance is computed as the running sum.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/admin/users/[userId]/actions.ts

@@ -59,6 +59,25 @@ export async function updateUserContact(
   revalidatePath(`/admin/users/${userId}`);
 }
 
+export async function addBalanceTransaction(
+  userId: string,
+  data: { amount: string; description: string }
+) {
+  await requireAdmin();
+  const amount = parseFloat(data.amount.replace(",", "."));
+  if (isNaN(amount) || amount === 0) throw new Error("Некорректная сумма");
+  await prisma.balanceTransaction.create({
+    data: { userId, amount, description: data.description.trim() },
+  });
+  revalidatePath(`/admin/users/${userId}`);
+}
+
+export async function deleteBalanceTransaction(userId: string, txId: string) {
+  await requireAdmin();
+  await prisma.balanceTransaction.delete({ where: { id: txId } });
+  revalidatePath(`/admin/users/${userId}`);
+}
+
 export async function revokeUserAccess(userId: string, courseId: string) {
   const session = await requireAdmin();
   await prisma.courseEnrollment.delete({

src/app/admin/users/[userId]/page.tsx

@@ -3,6 +3,7 @@ import { notFound } from "next/navigation";
 import Link from "next/link";
 import { UserEnrollmentManager } from "@/components/admin/user-enrollment-manager";
 import { UserContactEditor } from "@/components/admin/user-contact-editor";
+import { UserBalanceBlock } from "@/components/admin/user-balance-block";
 
 interface Props {
   params: Promise<{ userId: string }>;
@@ -27,6 +28,9 @@ export default async function UserPage({ params }: Props) {
             grantedBy: { select: { name: true } },
           },
         },
+        balanceTransactions: {
+          orderBy: { createdAt: "desc" },
+        },
       },
     }),
     prisma.course.findMany({
@@ -73,6 +77,22 @@ export default async function UserPage({ params }: Props) {
         </div>
       </section>
 
+      {/* Balance */}
+      <section className="card-aubade p-6 mb-6">
+        <p className="text-xs font-bold uppercase tracking-widest mb-5" style={{ color: "var(--muted-foreground)" }}>
+          Баланс
+        </p>
+        <UserBalanceBlock
+          userId={userId}
+          transactions={user.balanceTransactions.map((tx) => ({
+            id: tx.id,
+            amount: Number(tx.amount),
+            description: tx.description,
+            createdAt: tx.createdAt,
+          }))}
+        />
+      </section>
+
       {/* Enrollments + bulk grant */}
       <section className="card-aubade p-6 mb-6">
         <p className="text-xs font-bold uppercase tracking-widest mb-5" style={{ color: "var(--muted-foreground)" }}>