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-workflow/src/workflow_state.rs

@@ -0,0 +1,11 @@
+use erp_core::events::EventBus;
+use sea_orm::DatabaseConnection;
+
+/// Workflow-specific state extracted from the server's AppState via `FromRef`.
+///
+/// Contains the database connection and event bus needed by workflow handlers.
+#[derive(Clone)]
+pub struct WorkflowState {
+    pub db: DatabaseConnection,
+    pub event_bus: EventBus,
+}