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/dist/ai/ai.service.d.ts

@@ -7,8 +7,28 @@ export type CategorySuggestion = {
     confidence: 'high' | 'medium' | 'low';
     usedFallback: boolean;
 };
+export type AiIngredientMatchSuggestion = {
+    productId: number;
+    reason?: string;
+    confidence: 'high' | 'medium' | 'low';
+};
+export type AiSubstitutionSuggestion = {
+    productId: number;
+    reason?: string;
+    confidence: 'high' | 'medium' | 'low';
+};
 export declare class AiService {
     private readonly logger;
+    suggestIngredientMatches(rawIngredient: string, candidates: Array<{
+        id: number;
+        name: string;
+        canonicalName?: string | null;
+    }>): Promise<AiIngredientMatchSuggestion[]>;
+    suggestSubstitutions(rawIngredient: string, availableProducts: Array<{
+        id: number;
+        name: string;
+        canonicalName?: string | null;
+    }>): Promise<AiSubstitutionSuggestion[]>;
     suggestCategory(productName: string, categories: FlatCategory[]): Promise<CategorySuggestion>;
     private fallbackToOvrigt;
 }