feat: update Keepa and Stalker functionalities with enhanced price extraction logic and test cases

src/stalker.ts

@@ -1355,7 +1355,11 @@ function extractCurrentPrice(csv: unknown): number | null {
 
 function extractLatestPositiveKeepaPrice(history: unknown): number | null {
   if (!Array.isArray(history)) return null;
-  for (let i = history.length - 1; i >= 0; i--) {
+
+  // Keepa CSV histories are [time, value, time, value, ...]. Only odd indexes
+  // are prices; even indexes are Keepa timestamps and can look like huge prices.
+  for (let i = history.length - 1; i >= 1; i--) {
+    if (i % 2 === 0) continue;
     const value = extractNumber(history[i]);
     if (value != null && value > 0) return value / 100;
   }