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

src/lib/formatting/currency.ts

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+/**
+ * Formats an integer amount in cents to German Euro representation.
+ * Example: 249 -> "2,49 €"
+ */
+export function formatCurrency(cents: number | null | undefined): string {
+  if (cents === null || cents === undefined || isNaN(cents)) {
+    return '0,00 €';
+  }
+  return new Intl.NumberFormat('de-DE', {
+    style: 'currency',
+    currency: 'EUR',
+  }).format(cents / 100);
+}
+
+/**
+ * Calculates stock value in cents.
+ * For integer/package units: quantity * packagePriceCents
+ * For partial packages: (quantity / packageSize) * packagePriceCents
+ */
+export function calculateStockValueCents(
+  quantity: number,
+  packageSize: number,
+  packagePriceCents: number | null | undefined
+): number {
+  if (!packagePriceCents || packagePriceCents <= 0 || quantity <= 0) {
+    return 0;
+  }
+  if (packageSize <= 0) {
+    return Math.round(quantity * packagePriceCents);
+  }
+  const fraction = quantity / packageSize;
+  return Math.round(fraction * packagePriceCents);
+}
+
+/**
+ * Calculates base price (Grundpreis) per 1kg, 1l, 100g, or 1 Stück.
+ */
+export function calculateBasePrice(
+  priceCents: number,
+  packageSize: number,
+  packageUnit: string
+): { basePriceCents: number; basePriceUnit: string } {
+  if (packageSize <= 0) {
+    return { basePriceCents: priceCents, basePriceUnit: packageUnit };
+  }
+
+  const unitLower = packageUnit.toLowerCase().trim();
+
+  if (unitLower === 'g' || unitLower === 'gramm') {
+    // Standard base price per 1 kg (1000 g)
+    const basePriceCents = Math.round((priceCents / packageSize) * 1000);
+    return { basePriceCents, basePriceUnit: '1 kg' };
+  }
+
+  if (unitLower === 'ml' || unitLower === 'milliliter') {
+    // Standard base price per 1 l (1000 ml)
+    const basePriceCents = Math.round((priceCents / packageSize) * 1000);
+    return { basePriceCents, basePriceUnit: '1 l' };
+  }
+
+  if (unitLower === 'kg' || unitLower === 'kilogramm') {
+    const basePriceCents = Math.round(priceCents / packageSize);
+    return { basePriceCents, basePriceUnit: '1 kg' };
+  }
+
+  if (unitLower === 'l' || unitLower === 'liter') {
+    const basePriceCents = Math.round(priceCents / packageSize);
+    return { basePriceCents, basePriceUnit: '1 l' };
+  }
+
+  const basePriceCents = Math.round(priceCents / packageSize);
+  return { basePriceCents, basePriceUnit: `1 ${packageUnit}` };
+}