feat(plugin): Schema 缓存 — moka LRU Cache 消除 resolve_entity_info 重复查库

- 添加 moka 0.12 依赖到 erp-plugin 和 erp-server
- 重写 state.rs: 新增 EntityInfo (含 generated_fields) 和 moka Cache
- AppState 新增 plugin_entity_cache 字段
- data_service.rs: 旧 resolve_entity_info 保留兼容，新增 resolve_entity_info_cached

crates/erp-plugin/src/state.rs

@@ -1,5 +1,9 @@
+use std::time::Duration;
+
+use moka::sync::Cache;
 use sea_orm::DatabaseConnection;
 
+use erp_core::error::{AppError, AppResult};
 use erp_core::events::EventBus;
 
 use crate::engine::PluginEngine;
@@ -10,4 +14,39 @@ pub struct PluginState {
     pub db: DatabaseConnection,
     pub event_bus: EventBus,
     pub engine: PluginEngine,
+    /// Schema 缓存 — key: "{plugin_id}:{entity_name}:{tenant_id}"
+    pub entity_cache: Cache<String, EntityInfo>,
+}
+
+/// 缓存的实体信息
+#[derive(Clone, Debug)]
+pub struct EntityInfo {
+    pub table_name: String,
+    pub schema_json: serde_json::Value,
+    pub generated_fields: Vec<String>,
+}
+
+impl EntityInfo {
+    /// 从 schema_json 解析字段列表
+    pub fn fields(&self) -> AppResult<Vec<crate::manifest::PluginField>> {
+        let entity_def: crate::manifest::PluginEntity =
+            serde_json::from_value(self.schema_json.clone())
+                .map_err(|e| AppError::Internal(format!("解析 entity schema 失败: {}", e)))?;
+        Ok(entity_def.fields)
+    }
+}
+
+impl PluginState {
+    pub fn new(db: DatabaseConnection, event_bus: EventBus, engine: PluginEngine) -> Self {
+        let entity_cache = Cache::builder()
+            .max_capacity(1000)
+            .time_to_idle(Duration::from_secs(300))
+            .build();
+        Self {
+            db,
+            event_bus,
+            engine,
+            entity_cache,
+        }
+    }
 }