feat: Add function to ignore non-item lines in receipt parsing

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

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

@@ -173,11 +173,29 @@ function hasAnyLetter(value: string): boolean {
   return /[a-zåäö]/i.test(value);
 }
 
+function isIgnoredReceiptLine(value: string): boolean {
+  const normalized = value.trim().toLowerCase();
+  if (!normalized) return false;
+
+  // Rabatt- och betalningsrader ska aldrig bli varuposter.
+  if (/^rabatt\b/.test(normalized)) return true;
+  if (/^summa\b/.test(normalized)) return true;
+  if (/^moms\b/.test(normalized)) return true;
+  if (/^pant\b/.test(normalized)) return true;
+  if (/^att\s+betala\b/.test(normalized)) return true;
+  if (/^totalt\b/.test(normalized)) return true;
+  if (/^kort\b/.test(normalized)) return true;
+  if (/^kontant\b/.test(normalized)) return true;
+
+  return false;
+}
+
 function normalizeParsedItem(input: any): ParsedReceiptItemRaw | null {
   if (!input || typeof input !== 'object') return null;
 
   const rawName = typeof input.rawName === 'string' ? input.rawName.trim() : '';
   if (!rawName || !hasAnyLetter(rawName)) return null;
+  if (isIgnoredReceiptLine(rawName)) return null;
 
   const quantity = Number(input.quantity);
   if (!Number.isFinite(quantity) || quantity <= 0) return null;
@@ -203,6 +221,10 @@ function ruleBasedParseLine(line: string): ParsedReceiptItemRaw | null {
   const nameCandidate = extractNameCandidate(line);
   const rawName = nameCandidate ?? line;
 
+  if (isIgnoredReceiptLine(rawName)) {
+    return null;
+  }
+
   // Multipack: "3x120g", "2 x 1.5l"
   const multiPack = /(\d+)\s*[x×]\s*(\d+(?:[\.,]\d+)?)\s*(ml|cl|dl|l|g|kg)\b/i.exec(normalized);
   if (multiPack) {
@@ -272,6 +294,10 @@ export class ReceiptParsingService {
     const needsAI: string[] = [];
 
     for (const line of combinedLines) {
+      if (isIgnoredReceiptLine(line)) {
+        continue;
+      }
+
       const item = ruleBasedParseLine(line);
       if (item !== null) {
         resolved.push(item);