feat(client): 设备管理屏在线状态徽章 → StatusPill + golden

onlineBadge（在线/离线 圆点文字）→ StatusPill（圆点软底 pill，
success/okSoft 与 muted/infoSoft）；整屏 golden ×三主题（桌面+移动）入回归闸。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TSKEiHsvauyxYUW2itzUXX

client/lib/screens/devices/device_management_screen.dart

@@ -7,6 +7,7 @@ import '../../core/theme/context_tokens.dart';
 import '../../models/session.dart';
 import '../../providers/session_provider.dart';
 import '../../widgets/data_table_card.dart';
+import '../../widgets/kpi_card.dart';
 import '../../widgets/mobile_list_card.dart';
 
 /// 设备 / 状态管理：本店在线设备/会话列表。
@@ -81,20 +82,16 @@ class DeviceManagementScreen extends ConsumerWidget {
 
   Widget _buildTable(BuildContext context, WidgetRef ref,
       List<DeviceSession> sessions, bool canKick) {
-    Widget onlineBadge(bool online) => Row(
-          mainAxisSize: MainAxisSize.min,
-          children: [
-            Icon(Icons.circle,
-                size: 9,
-                color: online ? context.tokens.success : context.tokens.muted),
-            const SizedBox(width: 4),
-            Text(online ? '在线' : '离线',
-                style: TextStyle(
-                    fontSize: 13,
-                    color:
-                        online ? context.tokens.success : context.tokens.muted)),
-          ],
-        );
+    // 还原原型 .badge.b-在线/b-离线：圆点软底 pill。
+    Widget onlineBadge(bool online) => online
+        ? StatusPill(
+            label: '在线',
+            color: context.tokens.success,
+            background: context.tokens.okSoft)
+        : StatusPill(
+            label: '离线',
+            color: context.tokens.muted,
+            background: context.tokens.infoSoft);
 
     String fmt(DateTime? t) => t == null ? '-' : _fmt.format(t);