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/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "erp-workflow"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+erp-core.workspace = true
+tokio = { workspace = true, features = ["full"] }
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true }
+uuid = { workspace = true, features = ["v7", "serde"] }
+chrono = { workspace = true, features = ["serde"] }
+axum = { workspace = true }
+sea-orm = { workspace = true, features = ["sqlx-postgres", "runtime-tokio-rustls", "with-uuid", "with-chrono", "with-json"] }
+tracing = { workspace = true }
+anyhow.workspace = true
+thiserror.workspace = true
+utoipa = { workspace = true, features = ["uuid", "chrono"] }
+async-trait.workspace = true
+validator.workspace = true
+reqwest = { workspace = true, features = ["json"] }