Let Dashboard and wide Layout spread on 2xl screens

Dashboard now opts into `wide`, and the wide container scales from 1400
to 1800px at the 2xl breakpoint so content uses the extra room on big
monitors. Queue-load grid gains xl/2xl column counts for the new width.
Below 1536px nothing changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

client/src/pages/Dashboard.tsx

@@ -45,7 +45,7 @@ export default function Dashboard() {
   const maxSeverity = Math.max(...(a?.openBySeverity.map((r) => r.count) ?? [1]));
 
   return (
-    <Layout title="Dashboard" subheader={<p className="text-xs text-muted-foreground">Last 30 days</p>}>
+    <Layout wide title="Dashboard" subheader={<p className="text-xs text-muted-foreground">Last 30 days</p>}>
       {!a ? (
         <p className="py-16 text-center text-sm text-muted-foreground">Loading analytics…</p>
       ) : (
@@ -143,7 +143,7 @@ export default function Dashboard() {
             {a.queueByAssignee.length === 0 ? (
               <p className="text-xs text-muted-foreground">No open tickets right now.</p>
             ) : (
-              <div className="grid gap-2 md:grid-cols-2 lg:grid-cols-3">
+              <div className="grid gap-2 md:grid-cols-2 lg:grid-cols-3 xl:grid-cols-4 2xl:grid-cols-6">
                 {a.queueByAssignee
                   .slice()
                   .sort((x, y) => y.count - x.count)