feat: add isPrivate field to Product model and implement private product creation and retrieval

backend/src/products/products.service.ts

@@ -19,6 +19,7 @@ export class ProductsService {
     return this.prisma.product.findMany({
       where: {
         isActive: true,
+        isPrivate: false,
         ...(filters?.subcategory ? { subcategory: filters.subcategory } : {}),
         ...(filters?.tag
           ? { tags: { some: { tag: { name: filters.tag } } } }
@@ -33,6 +34,45 @@ export class ProductsService {
     });
   }
 
+  async findByOwner(userId: number) {
+    return this.prisma.product.findMany({
+      where: { ownerId: userId, isPrivate: true, isActive: true },
+      select: { id: true, name: true, canonicalName: true, categoryId: true },
+      orderBy: { name: 'asc' },
+    });
+  }
+
+  async createPrivate(data: CreateProductDto, userId: number) {
+    const name = data.name.trim();
+    // Privata produkters normalizedName är prefixade för att undvika kollision
+    const normalizedName = `private:${userId}:${normalizeName(name)}`;
+
+    const existing = await this.prisma.product.findUnique({
+      where: { normalizedName },
+    });
+
+    if (existing && existing.isActive) return existing;
+
+    if (existing) {
+      return this.prisma.product.update({
+        where: { id: existing.id },
+        data: { isActive: true, deletedAt: null, name, canonicalName: name },
+      });
+    }
+
+    return this.prisma.product.create({
+      data: {
+        name,
+        normalizedName,
+        canonicalName: name,
+        isActive: true,
+        isPrivate: true,
+        ownerId: userId,
+        ...(data.categoryId != null ? { categoryId: data.categoryId } : {}),
+      },
+    });
+  }
+
   async findDuplicateCandidates() {
     const products = await this.prisma.product.findMany({
       where: {
@@ -107,6 +147,7 @@ export class ProductsService {
         canonicalName: name,
         isActive: true,
         deletedAt: null,
+        ...(data.categoryId != null ? { categoryId: data.categoryId } : {}),
       },
     });
   }