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-cms/src/domain/mod.rs

@@ -1,7 +1,22 @@
-//! Domain layer — pure entities, repository traits, and service trait definitions.
+//! Domain layer — pure entities, value objects, repository traits, and service interfaces.
 //!
-//! This layer has zero infrastructure dependencies; all I/O is expressed through
-//! repository traits defined in [`repository`].
+//! This is the innermost layer of the Clean Architecture onion. It has **zero
+//! infrastructure dependencies** — all I/O is expressed through repository
+//! traits defined in [`repository`], and business operations through service
+//! traits in [`service`].
+//!
+//! ## Sub-modules
+//! - `app_config` — provider configuration model (`AppConfig`, `ProviderConfig`, `ModelRole`)
+//! - `conversation` — conversation entity + chat message model (`Conversation`, `ChatMessage`)
+//! - `edit_log` — edit log model (`EditLog`, `EditLogEntry`)
+//! - `memory` — memory file model (`Memory`)
+//! - `settings` — application settings model (`Settings`, `InternetMode`, `SettingsFlags`)
+//! - `repository` — trait definitions for all persistence adapters
+//! - `service` — trait definitions for all application services
+//!
+//! ## Key Design Principle
+//! Domain types are plain Rust structs with `serde` for serialisation.
+//! They contain no I/O, no framework imports, and no side effects.
 
 pub mod app_config;
 pub mod conversation;