fix: trend chart tooltip shows no data on hover

Replaced Recharts default Tooltip with formatter prop (broken in
Recharts v3 with explicit type annotations) with a custom
TrendTooltip component matching the SQL Explorer pattern. Shows
each series name, value, and color on hover.

frontend/src/pages/CompanyDetail.tsx

@@ -565,6 +565,23 @@ interface ChartPoint {
   window: string;
 }
 
+function TrendTooltip({ active, payload, label }: Record<string, unknown>) {
+  if (!active) return null;
+  const items = payload as Array<{ name: string; value: number; color: string }> | undefined;
+  if (!items?.length) return null;
+  return (
+    <div className="rounded-lg border border-surface-700 bg-surface-900 px-3 py-2 text-xs shadow-lg">
+      <div className="mb-1 text-gray-400">{String(label ?? '')}</div>
+      {items.map((item, i) => (
+        <div key={i} className="flex justify-between gap-4" style={{ color: item.color }}>
+          <span>{item.name}:</span>
+          <span className="font-semibold">{item.value}%</span>
+        </div>
+      ))}
+    </div>
+  );
+}
+
 function TrendHistoryChart({ trends, latestTrends, ticker }: { trends: TrendSummary[]; latestTrends: TrendSummary[]; ticker: string }) {
   const [selectedWindow, setSelectedWindow] = useState('7d');
 
@@ -640,11 +657,7 @@ function TrendHistoryChart({ trends, latestTrends, ticker }: { trends: TrendSumm
                   tickLine={{ stroke: '#475569' }}
                   tickFormatter={(v) => `${v}%`}
                 />
-                <Tooltip
-                  contentStyle={{ backgroundColor: '#1e293b', border: '1px solid #334155', borderRadius: '8px' }}
-                  labelStyle={{ color: '#94a3b8' }}
-                  formatter={(value, name) => [`${value}%`, name]}
-                />
+                <Tooltip content={TrendTooltip} />
                 <Legend wrapperStyle={{ color: '#94a3b8', fontSize: 12 }} />
                 <Line
                   type="monotone"