Add a title to the device usage table card on Stats

Matches the "History"/"Known devices" card-title pattern used on the
Sessions and Devices pages.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzyfRyA7h5rs5SCAahLAWd

components/stats/DeviceUsageTable.tsx

@@ -1,4 +1,4 @@
-import { Card, CardContent } from "@/components/ui/card";
+import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/components/ui/table";
 
 export interface DeviceUsageRow {
@@ -15,6 +15,9 @@ export function DeviceUsageTable({ devices }: { devices: DeviceUsageRow[] }) {
   if (devices.length === 0) {
     return (
       <Card className="bp-glass">
+        <CardHeader>
+          <CardTitle className="text-base">Device usage</CardTitle>
+        </CardHeader>
         <CardContent className="py-6 text-sm text-muted-foreground">No device activity yet.</CardContent>
       </Card>
     );
@@ -22,6 +25,9 @@ export function DeviceUsageTable({ devices }: { devices: DeviceUsageRow[] }) {
 
   return (
     <Card className="bp-glass">
+      <CardHeader>
+        <CardTitle className="text-base">Device usage</CardTitle>
+      </CardHeader>
       <CardContent>
         <Table>
           <TableHeader>