Add transaction rate and enhance chart tooltips

Added transaction-per-second (TPS) metric calculation to the TargetDetailPage and updated the chart to display it. Improved tooltip design and functionality for better readability, including dynamic metrics display and styled components.

frontend/src/styles.css

@@ -359,6 +359,37 @@ td {
   margin: 8px 0 0 18px;
 }
 
+.chart-tooltip {
+  background: #0f1934ee;
+  border: 1px solid #2f4a8b;
+  border-radius: 10px;
+  padding: 10px 12px;
+  min-width: 170px;
+}
+
+.chart-tooltip-time {
+  font-size: 12px;
+  color: #9cb2d8;
+  margin-bottom: 6px;
+}
+
+.chart-tooltip-item {
+  font-size: 14px;
+  margin: 3px 0;
+}
+
+.chart-tooltip-item.c1 {
+  color: #38bdf8;
+}
+
+.chart-tooltip-item.c2 {
+  color: #22c55e;
+}
+
+.chart-tooltip-item.c3 {
+  color: #f59e0b;
+}
+
 @media (max-width: 980px) {
   body {
     overflow: auto;