feat: enhance README and improve product data handling in cache, llm, reader, and writer modules

src/types.ts

@@ -5,14 +5,24 @@ export interface ProductRecord {
   brand?: string;
   category?: string;
   amazonRank?: number;
+  avgPrice90FromSheet?: number;
+  sellingPriceFromSheet?: number;
   fbaNet?: number;
   grossProfit?: number;
   grossProfitPct?: number;
+  netProfitFromSheet?: number;
+  roiFromSheet?: number;
   moq?: number;
   moqCost?: number;
   totalQtyAvail?: number;
 
   link?: string;
+  asinLink?: string;
+  sourceUrl?: string;
+  supplier?: string;
+  promoCouponCode?: string;
+  notes?: string;
+  leadDate?: string;
   [key: string]: unknown;
 }