fix: widen price matching tolerance for sparse market data

Only ~9 price bars per ticker (Polygon returns daily bars, not
intraday). Widened gap tolerance to 6h for intraday, 12h for 1d,
etc. Also skip time-range filtering when price data is sparse
(≤20 bars) to avoid showing no prices at all.

frontend/src/pages/CompanyDetail.tsx

@@ -703,8 +703,8 @@ function TrendHistoryChart({ trends, latestTrends, ticker, marketPrices, selecte
     .filter((p) => p.bar_timestamp != null && p.close != null)
     .sort((a, b) => a.bar_timestamp - b.bar_timestamp);
 
-  // Filter prices to the selected window's time range
+  // Filter prices to the selected window's time range (use all prices if sparse)
-  const windowPrices = sortedPrices.filter((p) => p.bar_timestamp >= cutoffTs);
+  const windowPrices = sortedPrices.length <= 20 ? sortedPrices : sortedPrices.filter((p) => p.bar_timestamp >= cutoffTs);
 
   function findClosestPrice(ts: number): number | undefined {
     if (windowPrices.length === 0) return undefined;
@@ -717,8 +717,16 @@ function TrendHistoryChart({ trends, latestTrends, ticker, marketPrices, selecte
         bestDiff = diff;
       }
     }
-    // Only match if within 2 hours (for intraday) or 36 hours (for daily)
+    // Match if within reasonable gap for the window type
-    const maxGap = selectedWindow === 'intraday' ? 2 * 3600_000 : 36 * 3600_000;
+    // With sparse price data (~1 bar per 4-6 hours), use wider tolerances
+    const maxGapHours: Record<string, number> = {
+      intraday: 6,
+      '1d': 12,
+      '7d': 36,
+      '30d': 72,
+      '90d': 168,
+    };
+    const maxGap = (maxGapHours[selectedWindow] ?? 36) * 3600_000;
     return bestDiff <= maxGap ? best.close : undefined;
   }