feat: implement receipt alias functionality with CRUD operations and integrate with receipt import

backend/src/receipt-alias/receipt-alias.service.ts

@@ -0,0 +1,28 @@
+import { Injectable } from '@nestjs/common';
+import { PrismaService } from '../prisma/prisma.service';
+import { CreateReceiptAliasDto } from './dto/create-receipt-alias.dto';
+
+@Injectable()
+export class ReceiptAliasService {
+  constructor(private readonly prisma: PrismaService) {}
+
+  findAll() {
+    return this.prisma.receiptAlias.findMany({
+      include: { product: { select: { id: true, name: true, canonicalName: true } } },
+      orderBy: { receiptName: 'asc' },
+    });
+  }
+
+  async upsert(dto: CreateReceiptAliasDto) {
+    const normalized = dto.receiptName.toLowerCase().trim();
+    return this.prisma.receiptAlias.upsert({
+      where: { receiptName: normalized },
+      create: { receiptName: normalized, productId: dto.productId },
+      update: { productId: dto.productId },
+    });
+  }
+
+  remove(id: number) {
+    return this.prisma.receiptAlias.delete({ where: { id } });
+  }
+}