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-server/tests/integration.rs

@@ -0,0 +1,8 @@
+#[path = "integration/auth_tests.rs"]
+mod auth_tests;
+#[path = "integration/plugin_tests.rs"]
+mod plugin_tests;
+#[path = "integration/test_db.rs"]
+mod test_db;
+#[path = "integration/workflow_tests.rs"]
+mod workflow_tests;