feat: Enhance tooltip behavior in ExpenseDonutChart to display formatted currency and percentage

lib/helpers/widgets/dashbaord/expense_breakdown_chart.dart

@@ -381,13 +381,45 @@ class _ExpenseDonutChartState extends State<_ExpenseDonutChart> {
     super.initState();
     _tooltipBehavior = TooltipBehavior(
       enable: true,
-      format: 'point.x: point.y',
-      color: Colors.blueAccent,
-      textStyle: const TextStyle(
-        color: Colors.white,
-        fontSize: 12,
-        fontWeight: FontWeight.w600,
-      ),
+      builder: (dynamic data, dynamic point, dynamic series, int pointIndex,
+          int seriesIndex) {
+        final total = widget.data.report
+            .fold<double>(0, (sum, e) => sum + e.totalApprovedAmount);
+        final value = data.value as double;
+        final percentage = total > 0 ? (value / total * 100) : 0;
+
+        return Container(
+          padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
+          decoration: BoxDecoration(
+            color: Colors.blueAccent,
+            borderRadius: BorderRadius.circular(4),
+          ),
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Text(
+                data.label,
+                style: const TextStyle(
+                    color: Colors.white, fontWeight: FontWeight.w600),
+              ),
+              const SizedBox(height: 2),
+              Text(
+                Utils.formatCurrency(value),
+                style: const TextStyle(
+                    color: Colors.white, fontWeight: FontWeight.w600),
+              ),
+              Text(
+                '${percentage.toStringAsFixed(1)}%',
+                style: const TextStyle(
+                    color: Colors.white70,
+                    fontWeight: FontWeight.w500,
+                    fontSize: 10),
+              ),
+            ],
+          ),
+        );
+      },
       elevation: 4,
       animationDuration: 300,
     );