feat: add updateCategoryMine endpoint to manage product category updates

- Implemented a new PATCH endpoint in ProductsController to update the category of a user's product.
- Added corresponding service method in ProductsService to handle business logic and validation.
- Created UpdateCategoryMineDto for request validation.
- Enhanced error handling for forbidden actions and not found resources.
- Updated API error mapping in Flutter to handle specific forbidden messages.
- Modified ProductPickerField to allow product creation directly from the picker.
- Added tests for the new endpoint and service method to ensure proper functionality and error handling.

backend/src/products/products.controller.ts

@@ -25,6 +25,7 @@ import { UpsertNutritionDto } from './dto/upsert-nutrition.dto';
 import { BulkUpdateProductsDto } from './dto/bulk-update-products.dto';
 import { AiCategorizeBulkDto } from './dto/ai-categorize-bulk.dto';
 import { SetProductStatusDto } from './dto/set-product-status.dto';
+import { UpdateCategoryMineDto } from './dto/update-category-mine.dto';
 import { Roles } from '../auth/decorators/roles.decorator';
 import { AiService } from '../ai/ai.service';
 import { CategoriesService } from '../categories/categories.service';
@@ -166,6 +167,15 @@ export class ProductsController {
     return this.productsService.mergePrivate(req.user.id, body.sourceProductId, body.targetProductId);
   }
 
+  @Patch('mine/:id/category')
+  updateCategoryMine(
+    @Param('id', ParseIntPipe) id: number,
+    @Body() body: UpdateCategoryMineDto,
+    @Request() req: { user: { id: number } },
+  ) {
+    return this.productsService.updateCategoryMine(req.user.id, id, body.categoryId);
+  }
+
   @Roles('admin')
   @Post('merge')
   merge(@Body() body: MergeProductsDto) {