feat: initialize Nuanji (Warm Notes) project

- Base platform from base.git (ERP base: auth, core, config, message, workflow, plugin)
- Created erp-diary module skeleton (lib.rs, dto.rs, error.rs, event.rs, state.rs)
- Integrated erp-diary into workspace and erp-server
- Added DiaryModule registration in main.rs
- Added DiaryState FromRef in state.rs
- Diary routes mounted (empty routes, ready for implementation)
- Product design spec v1.2 preserved in docs/
- Implementation plan preserved in plans/

Cargo check: OK
Cargo test: OK (78+ base tests passing)

crates/erp-plugin/src/entity/plugin_entity.rs

@@ -0,0 +1,43 @@
+use sea_orm::entity::prelude::*;
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Serialize, Deserialize)]
+#[sea_orm(table_name = "plugin_entities")]
+pub struct Model {
+    #[sea_orm(primary_key, auto_increment = false)]
+    pub id: Uuid,
+    pub tenant_id: Uuid,
+    pub plugin_id: Uuid,
+    pub entity_name: String,
+    pub table_name: String,
+    pub schema_json: serde_json::Value,
+    pub manifest_id: String,
+    pub is_public: bool,
+    pub created_at: DateTimeUtc,
+    pub updated_at: DateTimeUtc,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub created_by: Option<Uuid>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub updated_by: Option<Uuid>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub deleted_at: Option<DateTimeUtc>,
+    pub version: i32,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::plugin::Entity",
+        from = "Column::PluginId",
+        to = "super::plugin::Column::Id"
+    )]
+    Plugin,
+}
+
+impl Related<super::plugin::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Plugin.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}