feat: KitchenStock light UI, Gemma 31B AI, supermarket store filters & 130+ vegan products

tests/mocks/server-only.ts

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+// Dummy mock for Next.js 'server-only' package in Vitest environment
+export {};

tests/unit/ai.test.ts

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+import { describe, it, expect } from 'vitest';
+import { MockKitchenAiProvider } from '@/lib/ai/client';
+
+describe('MockKitchenAiProvider (No Billing Test)', () => {
+  const provider = new MockKitchenAiProvider();
+
+  it('suggests recipes with expected structured outputs', async () => {
+    const recipes = await provider.suggestRecipes({
+      householdId: 'test-household',
+      inventory: [
+        {
+          id: 'prod-1',
+          householdId: 'test-household',
+          categoryId: null,
+          defaultLocationId: null,
+          defaultUnitId: null,
+          name: 'Reis',
+          brand: null,
+          description: null,
+          barcode: null,
+          imagePath: null,
+          packageSize: 1000,
+          packageUnit: 'g',
+          minimumQuantity: 100,
+          favorite: true,
+          preferredStore: null,
+          estimatedPriceCents: 249,
+          priceUpdatedAt: null,
+          archived: false,
+          totalQuantity: 1000,
+          stockValueCents: 249,
+          isLowStock: false,
+          isExpiringSoon: false,
+          earliestExpirationDate: null,
+        },
+      ],
+    });
+
+    expect(recipes).toHaveLength(1);
+    expect(recipes[0].title).toBeDefined();
+    expect(recipes[0].inventoryCoveragePercent).toBeGreaterThan(0);
+  });
+
+  it('returns verified price searches via Mock Provider', async () => {
+    const price = await provider.searchPrices({
+      householdId: 'test-household',
+      query: 'Spaghetti',
+      retailer: 'REWE',
+    });
+
+    expect(price.priceCents).toBe(189);
+    expect(price.confidence).toBe('HIGH');
+  });
+});

tests/unit/currency.test.ts

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+import { describe, it, expect } from 'vitest';
+import { formatCurrency, calculateBasePrice, calculateStockValueCents } from '@/lib/formatting/currency';
+
+describe('Currency & Stock Value Formatting', () => {
+  it('formats integer cents into German Euro currency string', () => {
+    expect(formatCurrency(249)).toContain('2,49');
+    expect(formatCurrency(0)).toContain('0,00');
+    expect(formatCurrency(1299)).toContain('12,99');
+  });
+
+  it('calculates full package stock value correctly', () => {
+    // 2 packages @ 1,99 € (199 Cent) = 398 Cent
+    expect(calculateStockValueCents(2, 1, 199)).toBe(398);
+  });
+
+  it('calculates partial package stock value correctly (750g of 1000g @ 1,29 € = 0,97 €)', () => {
+    // 750g / 1000g * 129 Cent = 96.75 Cent -> rounded to 97 Cent
+    expect(calculateStockValueCents(750, 1000, 129)).toBe(97);
+  });
+
+  it('calculates base price (Grundpreis) per 1kg for grams', () => {
+    // 500g Barilla Spaghetti @ 1,89 € (189 Cent) -> 3.78 € / kg (378 Cent)
+    const base = calculateBasePrice(189, 500, 'g');
+    expect(base.basePriceCents).toBe(378);
+    expect(base.basePriceUnit).toBe('1 kg');
+  });
+});

tests/unit/date.test.ts

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+import { describe, it, expect } from 'vitest';
+import { formatDateGerman, getExpirationStatus } from '@/lib/formatting/date';
+
+describe('Date & Expiration Status Helpers', () => {
+  it('formats ISO dates into German TT.MM.JJJJ format', () => {
+    expect(formatDateGerman('2026-07-26')).toBe('26.07.2026');
+  });
+
+  it('returns OK for null expiration date', () => {
+    const status = getExpirationStatus(null);
+    expect(status.status).toBe('OK');
+    expect(status.label).toBe('Kein Ablaufdatum');
+  });
+
+  it('correctly flags expired dates', () => {
+    const status = getExpirationStatus('2020-01-01');
+    expect(status.status).toBe('EXPIRED');
+    expect(status.label).toContain('Abgelaufen');
+  });
+});