feat: add frontend dashboard for run results viewer

- Implemented main dashboard with run metrics and filtering options.
- Created detailed view for individual runs with results and anomalies.
- Added product listing page with filtering and pagination.
- Introduced utility functions for formatting dates and numbers.
- Styled components with CSS for a clean and responsive layout.
- Set up HTML entry point and linked to the main JavaScript file.
- Updated TypeScript configuration to include DOM types.

src/llm.ts

@@ -7,9 +7,14 @@ Given product data, evaluate each product's viability for selling on Amazon. Con
 
 1. **Sales Velocity**: monthlySold and salesRankDrops30 are the most important signals. A product that doesn't sell is worthless regardless of margin. salesRankDrops30 = approximate units sold in 30 days. monthlySold is Keepa's estimate.
 2. **Margin Analysis**: Sale price minus unit cost minus fees (FBA or FBM). Aim for >30% ROI minimum. The spreadsheet may include FBA NET and gross profit estimates — cross-check against Keepa pricing data.
+   - If unitCost is 0, it means NO COST DATA is available — this is NOT a free product. Do not assume infinite or zero-cost margins. When estimatedROI is null and unitCost is 0, evaluate purely on demand and velocity signals; never extrapolate profitability.
+   - If estimatedProfit is null, price data was unavailable at analysis time — treat as elevated uncertainty and be conservative.
 3. **Sales Rank (BSR)**: Lower rank = higher demand. Rank <50,000 is good, <1,000 is excellent.
 4. **Sales Rank Trend**: Compare current rank vs 90d average. Lower current = improving demand.
-5. **Competition**: Number of sellers and Buy Box dynamics. Fewer sellers = easier entry.
+5. **Competition & Buy Box**:
+   - Fewer sellers = easier entry, but verify who holds the Buy Box.
+   - If buyBoxSeller is "ATVPDKIKX0DER" (Amazon retail), the product is Amazon-exclusive — return "SKIP". Amazon-sold items cannot be competed with by third-party sellers.
+   - If sellerCount is 1 and buyBoxSeller is not null, assume the market is closed — return "SKIP".
 6. **Price Stability**: Large price swings (high max vs low min over 90d) = volatile/risky.
 7. **FBA vs FBM**: FBA preferred for fast-selling, small/light items. FBM for oversized, slow-moving, or high-margin items where fee savings matter.
 8. **MOQ & Capital**: High MOQ with thin margins is risky.
@@ -21,6 +26,7 @@ Given product data, evaluate each product's viability for selling on Amazon. Con
 
 Decision policy:
 - Do not recommend products that cannot be listed by this seller account.
+- Do not recommend Amazon-exclusive products (buyBoxSeller = "ATVPDKIKX0DER").
 - Prioritize profitable + high-velocity + listable products.
 - Use "SKIP" when data quality is poor or risk is high.
 
@@ -106,12 +112,20 @@ function summarizeForLlm(p: EnrichedProduct) {
   const salePrice =
     p.keepa?.currentPrice ??
     p.record.sellingPriceFromSheet ??
-    p.spApi.estimatedSalePrice;
-  const referralFee = salePrice * (p.spApi.referralFeePercent / 100);
+    (p.spApi.estimatedSalePrice > 0 ? p.spApi.estimatedSalePrice : null) ??
+    p.keepa?.avgPrice90 ??
+    null;
+
+  const referralFee =
+    salePrice != null ? salePrice * (p.spApi.referralFeePercent / 100) : null;
   const fbaProfit =
-    salePrice - p.record.unitCost - p.spApi.fbaFee - referralFee;
+    salePrice != null && referralFee != null
+      ? salePrice - p.record.unitCost - p.spApi.fbaFee - referralFee
+      : null;
   const fbmProfit =
-    salePrice - p.record.unitCost - p.spApi.fbmFee - referralFee;
+    salePrice != null && referralFee != null
+      ? salePrice - p.record.unitCost - p.spApi.fbmFee - referralFee
+      : null;
 
   return {
     asin: p.record.asin,
@@ -121,7 +135,7 @@ function summarizeForLlm(p: EnrichedProduct) {
       p.record.category ?? p.keepa?.categoryTree?.join(" > "),
       60,
     ),
-    unitCost: p.record.unitCost,
+    unitCost: p.record.unitCost > 0 ? p.record.unitCost : null,
     currentPrice: salePrice,
     priceRange90d: p.keepa
       ? {
@@ -133,6 +147,8 @@ function summarizeForLlm(p: EnrichedProduct) {
     salesRank: p.keepa?.salesRank ?? p.record.amazonRank,
     salesRankAvg90d: p.keepa?.salesRankAvg90,
     sellerCount: p.keepa?.sellerCount,
+    buyBoxSeller: p.keepa?.buyBoxSeller ?? null,
+    buyBoxPrice: p.keepa?.buyBoxPrice ?? null,
     salesVelocity: {
       monthlySold: p.keepa?.monthlySold,
       salesRankDrops30: p.keepa?.salesRankDrops30,
@@ -155,27 +171,28 @@ function summarizeForLlm(p: EnrichedProduct) {
       fbaFee: p.spApi.fbaFee,
       fbmFee: p.spApi.fbmFee,
       referralFeePercent: p.spApi.referralFeePercent,
-      referralFee: Math.round(referralFee * 100) / 100,
+      referralFee:
+        referralFee != null ? Math.round(referralFee * 100) / 100 : null,
     },
     sellerEligibility: {
       canSell: p.spApi.canSell,
       status: p.spApi.sellabilityStatus,
       reason: clampText(p.spApi.sellabilityReason, 120),
     },
-    estimatedProfit: {
-      fba: Math.round(fbaProfit * 100) / 100,
-      fbm: Math.round(fbmProfit * 100) / 100,
-    },
-    estimatedROI: {
-      fba:
-        p.record.unitCost > 0
-          ? Math.round((fbaProfit / p.record.unitCost) * 100)
-          : null,
-      fbm:
-        p.record.unitCost > 0
-          ? Math.round((fbmProfit / p.record.unitCost) * 100)
-          : null,
-    },
+    estimatedProfit:
+      fbaProfit != null && fbmProfit != null
+        ? {
+            fba: Math.round(fbaProfit * 100) / 100,
+            fbm: Math.round(fbmProfit * 100) / 100,
+          }
+        : null,
+    estimatedROI:
+      p.record.unitCost > 0 && fbaProfit != null && fbmProfit != null
+        ? {
+            fba: Math.round((fbaProfit / p.record.unitCost) * 100),
+            fbm: Math.round((fbmProfit / p.record.unitCost) * 100),
+          }
+        : null,
   };
 }