feat: add rematch functionality for recipe ingredients and enhance inventory management

- Added a new API path for rematching recipe ingredients in `api_paths.dart`.
- Implemented a manual product creation dialog in `inventory_screen.dart` to allow users to create new products directly.
- Integrated the rematch functionality in `recipe_repository.dart` to handle rematching of recipe ingredients.
- Updated the recipe detail screen to include a button for triggering the rematch process.
- Introduced a new `RecipeMatchingService` in the backend to handle ingredient matching logic.
- Added database migration to include `aiEngineEnabled` column in the User table.

Co-authored-by: Copilot <copilot@github.com>

backend/src/users/users.controller.ts

@@ -19,6 +19,11 @@ class SetRecipeSharingDto {
   canShareRecipes: boolean;
 }
 
+class SetAiEngineEnabledDto {
+  @IsBoolean()
+  aiEngineEnabled: boolean;
+}
+
 class AdminCreateUserDto {
   @IsString()
   @MinLength(2)
@@ -128,6 +133,16 @@ export class UsersController {
     return { id: updated.id, username: updated.username, canShareRecipes: updated.canShareRecipes };
   }
 
+  @Roles('admin')
+  @Patch(':id/ai-engine')
+  async setAiEngineEnabled(
+    @Param('id', ParseIntPipe) id: number,
+    @Body() dto: SetAiEngineEnabledDto,
+  ) {
+    const updated = await this.usersService.setAiEngineEnabled(id, dto.aiEngineEnabled);
+    return { id: updated.id, username: updated.username, aiEngineEnabled: updated.aiEngineEnabled };
+  }
+
   @Roles('admin')
   @Post()
   async adminCreateUser(

backend/src/users/users.service.ts

@@ -34,6 +34,7 @@ export class UsersService {
         role: true,
         isPremium: true,
         canShareRecipes: true,
+        aiEngineEnabled: true,
         createdAt: true,
       },
       orderBy: { username: 'asc' },
@@ -52,6 +53,10 @@ export class UsersService {
     return this.prisma.user.update({ where: { id }, data: { canShareRecipes } });
   }
 
+  setAiEngineEnabled(id: number, aiEngineEnabled: boolean) {
+    return this.prisma.user.update({ where: { id }, data: { aiEngineEnabled } });
+  }
+
   async adminCreate(data: { username: string; email: string; password: string; role?: string }) {
     const existing = await this.prisma.user.findFirst({
       where: { OR: [{ username: data.username }, { email: data.email }] },