fix: WorkflowPage UserDropdown selectedIds.map 报错 — 防御非数组值

- UserDropdown 组件加 Array.isArray(selectedIds) 防御
- 加载 workflow steps 时 approver_ids 加 try/catch 和类型判断
- 兼容后端返回 string/JSON/array/null 各种格式

frontend/src/pages/WorkflowPage.tsx

@@ -97,7 +97,8 @@ interface UserDropdownProps {
 
 function UserDropdown({ users, selectedIds, label, onToggle, onToggleAll, onClear, getUserName }: UserDropdownProps) {
   const [open, setOpen] = useState(false);
-  const allSelected = selectedIds.length === users.length && users.length > 0;
+  const ids = Array.isArray(selectedIds) ? selectedIds : [];
+  const allSelected = ids.length === users.length && users.length > 0;
 
   return (
     <div className="relative">
@@ -112,20 +113,20 @@ function UserDropdown({ users, selectedIds, label, onToggle, onToggleAll, onClea
         }`}
       >
         <span className="truncate">
-          {selectedIds.length === 0
+          {ids.length === 0
             ? `${label} * 请选择`
-            : selectedIds.length === 1
-              ? getUserName(selectedIds[0])
-              : `${label} (${selectedIds.length}人)`
+            : ids.length === 1
+              ? getUserName(ids[0])
+              : `${label} (${ids.length}人)`
           }
         </span>
         <ChevronDown className={`w-4 h-4 text-[var(--dg-text-muted)] transition-transform ${open ? 'rotate-180' : ''}`} />
       </button>
 
       {/* Selected tags */}
-      {selectedIds.length > 1 && (
+      {ids.length > 1 && (
         <div className="flex flex-wrap gap-1 mt-1.5">
-          {selectedIds.map((uid) => (
+          {ids.map((uid) => (
             <span
               key={uid}
               className="inline-flex items-center gap-1 px-1.5 py-0.5 rounded text-[11px] bg-blue-500/15 text-blue-400"
@@ -218,7 +219,7 @@ function WorkflowEditorModal({ workflow, users, onClose, onSaved }: EditorProps)
           step_type: (s.step_type === 'serial' || s.step_type === 'parallel' || s.step_type === 'any_one')
             ? 'audit' as const
             : s.step_type as 'submit' | 'audit' | 'execute',
-          approver_ids: s.approver_ids ? JSON.parse(s.approver_ids) : [],
+          approver_ids: Array.isArray(s.approver_ids) ? s.approver_ids : (s.approver_ids ? ((): number[] => { try { const p = JSON.parse(s.approver_ids as string); return Array.isArray(p) ? p : []; } catch { return []; } })() : []),
         }))
       );
     } else {