feat(k8s-ui): HPA 创建按钮醒目化 + K8sWorkloads 命名空间切换

DeploymentDetail:
  - HPA 未配置时，状态卡片内直接显示「创建 HPA」按钮
  - 无需切换到 HPA Tab 即可一键创建

K8sWorkloads:
  - 新增命名空间下拉选择器（自动加载集群全部 ns）
  - 切换集群时自动重置命名空间为「全部」
  - Deployment/Pod 列表按命名空间过滤
  - 统计卡片始终显示全量数据（不受 ns 过滤影响）

frontend/src/components/k8s/DeploymentDetail.tsx

@@ -220,7 +220,19 @@ export function DeploymentDetail({ clusterId, namespace, deploymentName, onBack
         <Card className="bg-slate-900 border-slate-800">
           <CardContent className="p-3">
             <p className="text-xs text-slate-500">HPA</p>
-            <p className="text-lg font-bold text-purple-400">{hpas.length > 0 ? '已启用' : '未配置'}</p>
+            {hpas.length > 0 ? (
+              <p className="text-lg font-bold text-purple-400">已启用</p>
+            ) : (
+              <div className="flex items-center justify-between">
+                <p className="text-lg font-bold text-slate-500">未配置</p>
+                <CreateHPADialog
+                  clusterId={clusterId}
+                  namespace={namespace}
+                  deploymentName={deploymentName}
+                  onCreated={loadData}
+                />
+              </div>
+            )}
           </CardContent>
         </Card>
       </div>

frontend/src/components/k8s/K8sWorkloads.tsx

@@ -22,6 +22,8 @@ export function K8sWorkloads() {
   const { toast } = useToast();
   const [clusters, setClusters] = useState<any[]>([]);
   const [selectedCluster, setSelectedCluster] = useState('');
+  const [namespaces, setNamespaces] = useState<string[]>([]);
+  const [selectedNamespace, setSelectedNamespace] = useState('all');
   const [deployments, setDeployments] = useState<any[]>([]);
   const [pods, setPods] = useState<any[]>([]);
   const [loading, setLoading] = useState(false);
@@ -43,6 +45,18 @@ export function K8sWorkloads() {
 
   useEffect(() => { loadClusters(); }, [loadClusters]);
 
+  // Load namespaces when cluster changes
+  const loadNamespaces = useCallback(async () => {
+    if (!selectedCluster) return;
+    try {
+      const res: any = await k8sApi.getNamespaces(selectedCluster);
+      const nsList: string[] = Array.isArray(res) ? res : (res?.list || res?.data || []);
+      setNamespaces(nsList);
+    } catch { setNamespaces([]); }
+  }, [selectedCluster]);
+
+  useEffect(() => { loadNamespaces(); }, [loadNamespaces]);
+
   const loadData = useCallback(async () => {
     if (!selectedCluster) return;
     setLoading(true);
@@ -60,10 +74,12 @@ export function K8sWorkloads() {
   useEffect(() => { loadData(); }, [loadData]);
 
   const filteredDeps = deployments.filter((d) =>
-    (d.name || '').toLowerCase().includes(search.toLowerCase()),
+    (d.name || '').toLowerCase().includes(search.toLowerCase()) &&
+    (selectedNamespace === 'all' || d.namespace === selectedNamespace),
   );
   const filteredPods = pods.filter((p) =>
-    (p.name || '').toLowerCase().includes(search.toLowerCase()),
+    (p.name || '').toLowerCase().includes(search.toLowerCase()) &&
+    (selectedNamespace === 'all' || p.namespace === selectedNamespace),
   );
 
   const getPodStatusBadge = (status: string) => {
@@ -112,7 +128,7 @@ export function K8sWorkloads() {
           <p className="text-sm text-slate-500 mt-1">Deployment 与 Pod 运行状态</p>
         </div>
         <div className="flex items-center gap-2">
-          <Select value={selectedCluster} onValueChange={setSelectedCluster}>
+          <Select value={selectedCluster} onValueChange={(v) => { setSelectedCluster(v); setSelectedNamespace('all'); }}>
             <SelectTrigger className="w-48 h-9 bg-slate-800/50 border-slate-700 text-slate-200">
               <SelectValue placeholder="选择集群" />
             </SelectTrigger>
@@ -122,6 +138,17 @@ export function K8sWorkloads() {
               ))}
             </SelectContent>
           </Select>
+          <Select value={selectedNamespace} onValueChange={setSelectedNamespace}>
+            <SelectTrigger className="w-40 h-9 bg-slate-800/50 border-slate-700 text-slate-200">
+              <SelectValue placeholder="命名空间" />
+            </SelectTrigger>
+            <SelectContent className="bg-slate-800 border-slate-700 max-h-[300px]">
+              <SelectItem value="all">全部命名空间</SelectItem>
+              {namespaces.map((ns) => (
+                <SelectItem key={ns} value={ns}>{ns}</SelectItem>
+              ))}
+            </SelectContent>
+          </Select>
           <Button variant="outline" size="icon" className="h-9 w-9 border-slate-700 text-slate-400" onClick={loadData} disabled={loading}>
             {loading ? <Loader2 className="h-4 w-4 animate-spin" /> : <RefreshCw className="h-4 w-4" />}
           </Button>