Fix fleet stale-status flicker during polling

src/lib/fleet-overview.ts

@@ -1,4 +1,5 @@
 import { parseServerName, zombieMapBySlug } from './map-aliases.js';
+import { freshStatusTimestamp } from './server-freshness.js';
 import type { ZombieGame } from './map-aliases.js';
 import type { RoundTelemetry } from './telemetry.js';
 import type { Health, RosterPlayer } from './ui/stores/servers.js';
@@ -40,8 +41,7 @@ export type FleetFilter = 'all' | 'occupied' | 'empty' | 'attention' | 'testing'
 export type FleetSort = 'name' | 'players' | 'round' | 'duration';
 
 export function freshServer(server: FleetServer, now: number): boolean {
-    const age = now - Date.parse(server.last_seen_at ?? '');
-    return server.health === 'online' && age >= 0 && age <= 30_000;
+    return server.health === 'online' && !server.last_error && freshStatusTimestamp(server.last_seen_at, now);
 }
 
 export function fleetIdentity(server: FleetServer) {