feat(receipt-import): add rule-based category suggestion logic for items

feat(migrations): add new categories for lactose-free products and allergy options

backend/src/receipt-import/receipt-import.service.ts

@@ -6,7 +6,7 @@ import {
 } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
 import { ParsedReceiptItem } from './dto/parsed-receipt-item.dto';
-import { AiService } from '../ai/ai.service';
+import { AiService, CategorySuggestion } from '../ai/ai.service';
 import { CategoriesService } from '../categories/categories.service';
 
 const IMPORTER_SERVICE_URL =
@@ -32,6 +32,15 @@ function tokenize(value: string): string[] {
     .filter((w) => w.length >= 3);
 }
 
+function normalizeForRules(value: string): string {
+  return value
+    .toLowerCase()
+    .normalize('NFD')
+    .replace(/[\u0300-\u036f]/g, '')
+    .replace(/[^a-z0-9]+/g, ' ')
+    .trim();
+}
+
 @Injectable()
 export class ReceiptImportService {
   private readonly logger = new Logger(ReceiptImportService.name);
@@ -221,6 +230,12 @@ export class ReceiptImportService {
     const enriched = new Map<string, ParsedReceiptItem>();
     for (const item of unmatched) {
       try {
+        const byRule = this.ruleBasedCategorySuggestion(item.rawName, categories);
+        if (byRule) {
+          enriched.set(item.rawName, { ...item, categorySuggestion: byRule });
+          continue;
+        }
+
         const suggestion = await this.aiService.suggestCategory(item.rawName, categories);
         enriched.set(item.rawName, { ...item, categorySuggestion: suggestion });
       } catch {
@@ -231,4 +246,61 @@ export class ReceiptImportService {
 
     return items.map((item) => enriched.get(item.rawName) ?? item);
   }
+
+  private ruleBasedCategorySuggestion(
+    rawName: string,
+    categories: Awaited<ReturnType<CategoriesService['findFlattened']>>,
+  ): CategorySuggestion | null {
+    const normalized = normalizeForRules(rawName);
+
+    const isCookingBase =
+      /\bmatlagningsbas\b/.test(normalized) ||
+      /\bmatlagnings\b/.test(normalized) ||
+      /\bplant\s+cream\b/.test(normalized) ||
+      /\bcreme\s+fraiche\b/.test(normalized) ||
+      /\bgradde\b/.test(normalized) ||
+      /\bvispgradde\b/.test(normalized);
+
+    const isPlantOrAllergy =
+      /\blaktosfri\b/.test(normalized) ||
+      /\bvegetabilisk\b/.test(normalized) ||
+      /\bhavre\b/.test(normalized) ||
+      /\bsoja\b/.test(normalized) ||
+      /\brisdryck\b/.test(normalized) ||
+      /\bplant\b/.test(normalized);
+
+    if (!isCookingBase || !isPlantOrAllergy) return null;
+
+    const l3AllergyCooking = categories.find(
+      (c) =>
+        c.name.toLowerCase() === 'allergi matlagning' &&
+        c.path.toLowerCase().startsWith('matlagning > '),
+    );
+    if (l3AllergyCooking) {
+      return {
+        categoryId: l3AllergyCooking.id,
+        categoryName: l3AllergyCooking.name,
+        path: l3AllergyCooking.path,
+        confidence: 'high',
+        usedFallback: false,
+      };
+    }
+
+    const l2Cooking = categories.find(
+      (c) =>
+        c.name.toLowerCase() === 'matlagning' &&
+        c.path.toLowerCase() === 'mejeri, ost & ägg > matlagning',
+    );
+    if (l2Cooking) {
+      return {
+        categoryId: l2Cooking.id,
+        categoryName: l2Cooking.name,
+        path: l2Cooking.path,
+        confidence: 'medium',
+        usedFallback: false,
+      };
+    }
+
+    return null;
+  }
 }