fix: escape arrow operator in conntrack flow display and remove push trigger from CI workflow

Remove push event trigger from GitHub Actions CI workflow to run only on pull requests, wrap arrow operator in curly braces to prevent JSX parsing issues in conntrack flow source/destination display

frontend/src/pages/Nodes.tsx

@@ -168,7 +168,7 @@ export function Nodes() {
                   const flow = item as Record<string, unknown>;
                   return (
                     <div key={index} className="border-b border-border px-3 py-2 text-xs last:border-0">
-                      <div className="font-medium">{String(flow.source_ip)}:{String(flow.source_port ?? "")} -> {String(flow.destination_ip)}:{String(flow.destination_port ?? "")}</div>
+                      <div className="font-medium">{String(flow.source_ip)}:{String(flow.source_port ?? "")} {"->"} {String(flow.destination_ip)}:{String(flow.destination_port ?? "")}</div>
                       <div className="text-slate-500">{String(flow.protocol ?? "unknown")} · {String(flow.bytes ?? 0)} bytes · {String(flow.packets ?? 0)} packets · {String(flow.state ?? "unknown")}</div>
                     </div>
                   );