feat(crm,inventory): P1 验证 — 插件 manifest 跨插件引用声明

- CRM: customer 实体新增 is_public = true，允许其他插件引用
- 进销存: sales_order.customer_id 新增 ref_plugin/ref_entity/ref_label_field/ref_fallback_label
- 进销存: metadata 版本升至 0.2.0，dependencies 添加 erp-crm

crates/erp-plugin-inventory/plugin.toml

@@ -1,10 +1,11 @@
 [metadata]
 id = "erp-inventory"
 name = "进销存管理"
-version = "0.1.0"
+version = "0.2.0"
 description = "进销存管理插件 — 产品、仓库、库存、供应商、采购单、销售单"
 author = "ERP Team"
 min_platform_version = "0.1.0"
+dependencies = ["erp-crm"]
 
 # ── 权限声明 ──
 
@@ -294,6 +295,12 @@ display_name = "销售单"
   name = "customer_id"
   field_type = "uuid"
   display_name = "客户"
+  ui_widget = "entity_select"
+  ref_plugin = "erp-crm"
+  ref_entity = "customer"
+  ref_label_field = "name"
+  ref_search_fields = ["name", "code"]
+  ref_fallback_label = "CRM 客户"
 
   [[schema.entities.fields]]
   name = "total_amount"