Enhance Tooltip labelFormatter for better handling (ref: gommzystudio#61; #4b18d31fc144b404b3a00905806cab0dc4a62b0f)

Author: fazelukario

client/src/components/ContactCard.tsx

@@ -186,7 +186,11 @@ export function ContactCard({
                                     <XAxis dataKey="timestamp" hide />
                                     <YAxis domain={['auto', 'auto']} />
                                     <Tooltip
-                                        labelFormatter={(t: number) => new Date(t).toLocaleTimeString()}
+                                        labelFormatter={(label) => {
+                                            const t = typeof label === "number" ? label : Number(label);
+                                            if (!Number.isFinite(t)) return String(label ?? "");
+                                            return new Date(t).toLocaleTimeString();
+                                        }}
                                         contentStyle={{ borderRadius: '8px', border: 'none', boxShadow: '0 4px 6px -1px rgb(0 0 0 / 0.1)' }}
                                     />
                                     <Line type="monotone" dataKey="avg" stroke="#3b82f6" strokeWidth={2} dot={false} name="Avg RTT" isAnimationActive={false} />