feat: Integrate Amazon SP-API for product sellability and pricing

- Added `amazon-sp-api` dependency to package.json.
- Enhanced configuration to include SP-API credentials and settings.
- Implemented SP-API client initialization and error handling in sp-api.ts.
- Developed functions to fetch product sellability and pricing data.
- Updated main processing logic in index.ts to incorporate sellability checks before fetching pricing.
- Modified LLM analysis to account for sellability status and reasons.
- Created a new sp-test.ts script for testing SP-API connectivity and sellability.
- Updated types.ts to define SellabilityInfo and extend SpApiData.
- Enhanced result reporting in writer.ts to include sellability information.

src/writer.ts

@@ -44,6 +44,14 @@ function buildRow(r: AnalysisResult) {
     "FBA Fee": r.product.spApi.fbaFee,
     "FBM Fee": r.product.spApi.fbmFee,
     "Referral %": r.product.spApi.referralFeePercent,
+    "Can Sell":
+      r.product.spApi.canSell == null
+        ? "unknown"
+        : r.product.spApi.canSell
+          ? "yes"
+          : "no",
+    Sellability: r.product.spApi.sellabilityStatus,
+    "Sellability Reason": r.product.spApi.sellabilityReason ?? "",
     Verdict: r.verdict.verdict,
     Confidence: r.verdict.confidence,
     Reasoning: r.verdict.reasoning,
@@ -90,6 +98,16 @@ export function printResults(results: AnalysisResult[]): void {
         "Net Profit": netProfit,
         "Monthly Sold": r.product.keepa?.monthlySold ?? "",
         "Sold 90 Day": r.product.keepa?.salesRankDrops90 ?? "",
+        "Can Sell":
+          r.product.spApi.canSell == null
+            ? "unknown"
+            : r.product.spApi.canSell
+              ? "yes"
+              : "no",
+        Sellability: r.product.spApi.sellabilityStatus,
+        "Sellability Reason": String(
+          r.product.spApi.sellabilityReason ?? "",
+        ).slice(0, 60),
         Confidence: r.verdict.confidence,
         Reasoning: r.verdict.reasoning.slice(0, 60),
       };
@@ -106,10 +124,25 @@ export function printResults(results: AnalysisResult[]): void {
     FBA: results.filter((r) => r.verdict.verdict === "FBA").length,
     FBM: results.filter((r) => r.verdict.verdict === "FBM").length,
     SKIP: results.filter((r) => r.verdict.verdict === "SKIP").length,
+    Available: results.filter(
+      (r) => r.product.spApi.sellabilityStatus === "available",
+    ).length,
+    Restricted: results.filter(
+      (r) => r.product.spApi.sellabilityStatus === "restricted",
+    ).length,
+    NotAvailable: results.filter(
+      (r) => r.product.spApi.sellabilityStatus === "not_available",
+    ).length,
+    Unknown: results.filter(
+      (r) => r.product.spApi.sellabilityStatus === "unknown",
+    ).length,
   };
   console.log(
     `\nSummary: ${summary.FBA} FBA | ${summary.FBM} FBM | ${summary.SKIP} SKIP out of ${results.length} products\n`,
   );
+  console.log(
+    `Sellability: ${summary.Available} available | ${summary.Restricted} restricted | ${summary.NotAvailable} not_available | ${summary.Unknown} unknown\n`,
+  );
 }
 
 export function writeResultsCsv(