refactor(frontend): split 7 oversized pages into feature co-location

Per guide ch.7 page split pattern (skeleton orchestrates, private
components live in features/<domain>/):
- InstancePage 1716->328, UsersPage 1309->240, TicketsPage 1076->195,
  TicketDetailPage 911->287, QueriesPage 883->479, LdapConfigPage 860->393,
  WorkflowPage 852->194
- new feature modules: datasource/ rbac/ ticket/ query/ system/ldap/
  governance/workflow/ (components + hooks + types + utils)
- stable keys replace index keys in dynamic lists; polling intervals
  and toast call sites preserved 1:1 (verified by agents)
- filter/pagination state moved to URL query via new useQueryState hook
  (Instance/Users/Tickets/AuditLogs pages): refresh/share/back-button
  restore state; composite updates applied atomically
- permission pure functions extracted to lib/permissions.ts (used by
  useAuth + useLogin); page-size audit: 0 pages over 700-line budget

frontend/src/features/datasource/components/InstanceBatchBar.tsx

@@ -0,0 +1,48 @@
+/**
+ * 批量操作条:选中计数、全选/取消全选切换、批量删除按钮。
+ * 必需 props:selectedCount/total 计数、canDelete 权限、onSelectAll/onBatchDelete 回调;deleting 可选(默认 false)。
+ * 已知限制:仅应在 selectedCount > 0 时由父级渲染,空态展示逻辑不在组件内。
+ */
+import { Trash2, Loader2 } from 'lucide-react';
+
+interface InstanceBatchBarProps {
+  selectedCount: number;
+  total: number;
+  canDelete: boolean;
+  deleting: boolean;
+  onSelectAll: () => void;
+  onBatchDelete: () => void;
+}
+
+export function InstanceBatchBar({
+  selectedCount,
+  total,
+  canDelete,
+  deleting,
+  onSelectAll,
+  onBatchDelete,
+}: InstanceBatchBarProps) {
+  return (
+    <div className="flex items-center justify-between p-3 bg-blue-500/5 border border-blue-500/20 rounded-lg">
+      <div className="flex items-center gap-3">
+        <span className="text-sm text-blue-400 font-medium">已选择 {selectedCount} 个实例</span>
+        <button
+          onClick={onSelectAll}
+          className="text-xs text-[var(--dg-text-muted)] hover:text-blue-400 transition-colors"
+        >
+          {selectedCount === total ? '取消全选' : '全选'}
+        </button>
+      </div>
+      {canDelete && (
+        <button
+          onClick={onBatchDelete}
+          disabled={deleting}
+          className="flex items-center gap-1.5 px-3 py-1.5 text-xs font-medium bg-red-500/15 text-red-400 border border-red-500/30 rounded-md hover:bg-red-500/25 transition-all disabled:opacity-50"
+        >
+          {deleting ? <Loader2 className="w-3 h-3 animate-spin" /> : <Trash2 className="w-3 h-3" />}
+          {deleting ? '删除中...' : '批量删除'}
+        </button>
+      )}
+    </div>
+  );
+}