feat: add supplier scoring and UPC file analysis functionality

- Implemented supplier scoring logic in `supplier-scoring.ts` with functions to compute demand score, competition penalty, and overall supplier product score.
- Created unit tests for supplier scoring in `supplier-scoring.test.ts` to validate scoring logic against various scenarios.
- Developed UPC file analysis tool in `upc-file-analysis.ts` to process UPCs in batches, fetch product data from Keepa and SP-API, and generate supplier results.
- Added UPC input reading functionality in `upc-file-reader.ts` to handle XLSX and XLS files, including validation for UPC formats.
- Introduced a command-line tool in `upc-lookup.ts` for looking up UPCs and displaying detailed results or mappings to ASINs.
- Enhanced error handling and logging throughout the new modules for better traceability and user feedback.

src/supplier/supplier-scoring.test.ts

@@ -0,0 +1,97 @@
+import { expect, test } from "bun:test";
+import { scoreSupplierProduct } from "./supplier-scoring.ts";
+import type { KeepaData, ProductRecord, SpApiData } from "../types.ts";
+
+function record(overrides: Partial<ProductRecord> = {}): ProductRecord {
+  return {
+    asin: "B000000001",
+    name: "Test Product",
+    unitCost: 10,
+    ...overrides,
+  };
+}
+
+function keepa(overrides: Partial<KeepaData> = {}): KeepaData {
+  return {
+    currentPrice: 30,
+    avgPrice90: 29,
+    minPrice90: 25,
+    maxPrice90: 35,
+    salesRank: 8_000,
+    salesRankAvg90: 10_000,
+    salesRankDrops30: 80,
+    salesRankDrops90: 220,
+    sellerCount: 4,
+    amazonIsSeller: false,
+    amazonBuyboxSharePct90d: 0,
+    buyBoxSeller: "SELLER",
+    buyBoxPrice: 30,
+    buyBoxAvg90: 29,
+    monthlySold: 350,
+    categoryTree: ["Grocery"],
+    ...overrides,
+  };
+}
+
+function spApi(overrides: Partial<SpApiData> = {}): SpApiData {
+  return {
+    fbaFee: 5,
+    fbmFee: 3,
+    referralFeePercent: 15,
+    estimatedSalePrice: 30,
+    canSell: true,
+    sellabilityStatus: "available",
+    sellabilityReason: "ok",
+    ...overrides,
+  };
+}
+
+test("profitable high-demand product ranks above competitive product", () => {
+  const strong = scoreSupplierProduct(record(), keepa(), spApi());
+  const competitive = scoreSupplierProduct(
+    record(),
+    keepa({
+      sellerCount: 35,
+      amazonIsSeller: true,
+      amazonBuyboxSharePct90d: 90,
+    }),
+    spApi(),
+  );
+
+  expect(strong.verdict).toBe("BUY");
+  expect(strong.score).toBeGreaterThan(competitive.score);
+});
+
+test("missing cost skips", () => {
+  const score = scoreSupplierProduct(record({ unitCost: 0 }), keepa(), spApi());
+
+  expect(score.verdict).toBe("SKIP");
+  expect(score.reason).toContain("unit cost");
+});
+
+test("restricted ASIN skips", () => {
+  const score = scoreSupplierProduct(
+    record(),
+    keepa(),
+    spApi({ canSell: false, sellabilityStatus: "restricted" }),
+  );
+
+  expect(score.verdict).toBe("SKIP");
+  expect(score.reason).toContain("restricted");
+});
+
+test("missing price skips", () => {
+  const score = scoreSupplierProduct(
+    record(),
+    keepa({
+      currentPrice: null,
+      avgPrice90: null,
+      buyBoxPrice: null,
+      buyBoxAvg90: null,
+    }),
+    spApi({ estimatedSalePrice: 0 }),
+  );
+
+  expect(score.verdict).toBe("SKIP");
+  expect(score.reason).toContain("price");
+});