feat(web,plugin): P1 跨插件引用 — 前端 Phase 4

- plugins.ts: PluginFieldSchema 新增 ref_plugin/ref_fallback_label, PluginEntitySchema 新增 is_public
- pluginData.ts: 新增 resolveRefLabels/getPluginEntityRegistry API
- EntitySelect: 支持 refPlugin 跨插件查询，目标不可用时降级为禁用 Input
- PluginCRUDPage: 表格列解析引用标签（蓝色 Tag），entity_select 表单传 refPlugin/fallbackLabel

apps/web/src/components/EntitySelect.tsx

@@ -1,4 +1,5 @@
-import { Select, Spin } from 'antd';
+import { Select, Spin, Input, Tooltip } from 'antd';
+import { QuestionCircleOutlined } from '@ant-design/icons';
 import { useState, useEffect, useCallback } from 'react';
 import { listPluginData } from '../api/pluginData';
 
@@ -7,6 +8,10 @@ interface EntitySelectProps {
   entity: string;
   labelField: string;
   searchFields?: string[];
+  /** 跨插件引用的目标插件 manifest ID（如 "erp-crm"） */
+  refPlugin?: string;
+  /** 目标插件未安装时的降级显示文本 */
+  fallbackLabel?: string;
   value?: string;
   onChange?: (value: string, label: string) => void;
   cascadeFrom?: string;
@@ -20,6 +25,8 @@ export default function EntitySelect({
   entity,
   labelField,
   searchFields: _searchFields,
+  refPlugin,
+  fallbackLabel,
   value,
   onChange,
   cascadeFrom,
@@ -29,6 +36,10 @@ export default function EntitySelect({
 }: EntitySelectProps) {
   const [options, setOptions] = useState<{ value: string; label: string }[]>([]);
   const [loading, setLoading] = useState(false);
+  const [targetUnavailable, setTargetUnavailable] = useState(false);
+
+  // 跨插件时使用目标插件 ID 查询
+  const effectivePluginId = refPlugin || pluginId;
 
   const fetchData = useCallback(
     async (keyword?: string) => {
@@ -39,7 +50,7 @@ export default function EntitySelect({
             ? { [cascadeFilter]: cascadeValue }
             : undefined;
 
-        const result = await listPluginData(pluginId, entity, 1, 20, {
+        const result = await listPluginData(effectivePluginId, entity, 1, 20, {
           search: keyword,
           filter,
         });
@@ -49,17 +60,39 @@ export default function EntitySelect({
           label: String(item.data?.[labelField] ?? item.id),
         }));
         setOptions(items);
+        setTargetUnavailable(false);
+      } catch {
+        if (refPlugin) {
+          setTargetUnavailable(true);
+          setOptions([]);
+        }
       } finally {
         setLoading(false);
       }
     },
-    [pluginId, entity, labelField, cascadeFrom, cascadeFilter, cascadeValue],
+    [effectivePluginId, entity, labelField, cascadeFrom, cascadeFilter, cascadeValue, refPlugin],
   );
 
   useEffect(() => {
     fetchData();
   }, [fetchData]);
 
+  // 目标插件未安装 → 降级显示
+  if (targetUnavailable) {
+    return (
+      <Input
+        value={value || ''}
+        placeholder={fallbackLabel || `外部引用 (${refPlugin})`}
+        disabled
+        suffix={
+          <Tooltip title="目标插件未安装，此字段暂时不可用">
+            <QuestionCircleOutlined style={{ color: '#999' }} />
+          </Tooltip>
+        }
+      />
+    );
+  }
+
   return (
     <Select
       showSearch