Remove chart hover effect

Removed the background color change on hover in the monthly comparison chart.

src/components/analytics/MonthlyComparisonChart.tsx

@@ -72,7 +72,11 @@ const MonthlyComparisonChart: React.FC<MonthlyComparisonChartProps> = ({
           }}>
             <XAxis dataKey="name" />
             <YAxis tickFormatter={formatYAxisTick} />
-            <Tooltip formatter={formatTooltip} />
+            <Tooltip 
+              formatter={formatTooltip} 
+              contentStyle={{ backgroundColor: 'white', border: 'none' }}
+              cursor={{ fill: 'transparent' }}
+            />
             <Legend />
             <Bar dataKey="budget" name="예산" fill="#C8C8C9" radius={[4, 4, 0, 0]} />
             <Bar dataKey="expense" name="지출" radius={[4, 4, 0, 0]}>