docs: tambah doc comment, logging, dan inline comments di semua 255 file

Meliputi:
- File-level //! doc comment: tujuan file, alur kerja, komponen utama
- Function-level /// doc comment: apa, parameter, return, flow, edge cases
- Struct/enum/trait /// doc comment: peran, field docs
- Tracing logging (tracing::info!/debug!/trace!/warn!/error!) di setiap fungsi
- Inline comments untuk variable dan branching logic penting
- Seluruh 8 crates di workspace: zesdex-backend, zesdex-cms, zesdex-entities,
  zesdex-iam, zesdex-infra, zesdex-ipc, zesdex-middleware, zesdex-utils
- Build: 0 errors, 242/242 tests passed

crates/zesdex-iam/src/domain/service.rs

@@ -1,5 +1,13 @@
 //! Service trait definitions — use-case interfaces for session management
 //! and OAuth flows.
+//!
+//! These traits define the boundary between the application orchestration
+//! layer and the domain. Implementations live in `application/`.
+//!
+//! # Traits
+//!
+//! - [`SessionService`] — create, list, archive sessions
+//! - [`OAuthService`] — start PKCE flow, complete code exchange, retrieve token
 use crate::domain::oauth::{OAuthConfig, OAuthToken};
 use crate::domain::session::Session;