feat: implement AI categorization for products and add premium access guard

backend/src/products/products.service.ts

@@ -4,10 +4,16 @@ import { normalizeName } from '../common/utils/normalize-name';
 import { CreateProductDto } from './dto/create-product.dto';
 import { UpdateProductDto } from './dto/update-product.dto';
 import { UpsertNutritionDto } from './dto/upsert-nutrition.dto';
+import { AiService } from '../ai/ai.service';
+import { CategoriesService } from '../categories/categories.service';
 
 @Injectable()
 export class ProductsService {
-  constructor(private readonly prisma: PrismaService) {}
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly aiService: AiService,
+    private readonly categoriesService: CategoriesService,
+  ) {}
 
   async findAll(filters?: { tag?: string; subcategory?: string }) {
     return this.prisma.product.findMany({
@@ -423,6 +429,25 @@ export class ProductsService {
     });
   }
 
+  async aiCategorizeBulk(productIds?: number[]): Promise<{ productId: number; productName: string; suggestion: object }[]> {
+    const categories = await this.categoriesService.findFlattened();
+    let products: { id: number; name: string }[];
+
+    if (productIds && productIds.length > 0) {
+      const found = await Promise.all(productIds.map((id) => this.findOne(id)));
+      products = found.map((p) => ({ id: p.id, name: p.canonicalName ?? p.name }));
+    } else {
+      products = await this.findUncategorized();
+    }
+
+    const results: { productId: number; productName: string; suggestion: object }[] = [];
+    for (const product of products) {
+      const suggestion = await this.aiService.suggestCategory(product.name, categories);
+      results.push({ productId: product.id, productName: product.name, suggestion });
+    }
+    return results;
+  }
+
   async findPending() {
     return this.prisma.product.findMany({
       where: { status: 'pending' },