Fix false stale Fleet reports caused by clock skew

src/lib/ui/components/ServerCard.svelte

@@ -54,9 +54,9 @@
         mapLabelOverride
     }: Props = $props();
 
-    function ago(iso: string | null): string {
+    function ago(iso: string | null, now: number): string {
         if (!iso) return 'never';
-        const d = Date.now() - new Date(iso).getTime();
+        const d = now - new Date(iso).getTime();
         if (d < 60_000) return `${Math.max(1, Math.floor(d / 1000))}s ago`;
         if (d < 3_600_000) return `${Math.floor(d / 60_000)}m ago`;
         if (d < 86_400_000) return `${Math.floor(d / 3_600_000)}h ago`;
@@ -175,9 +175,9 @@
         {#if health === 'offline' && lastError}
             <span class="err">{lastError}</span>
         {:else if lastSeenAt}
-            <span>Last seen {ago(lastSeenAt)}</span>
+            <span>Last seen {ago(lastSeenAt, $uiNow)}</span>
         {:else if lastRestartedAt}
-            <span>Restart {ago(lastRestartedAt)}</span>
+            <span>Restart {ago(lastRestartedAt, $uiNow)}</span>
         {:else}
             <span class="dim">No data</span>
         {/if}