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-entities/src/domain/common/conversation.rs

@@ -1,17 +1,39 @@
 //! In-memory conversation state: message history plus the system prompt and
 //! model parameters used to drive the LLM.
+//!
+//! # Flow
+//!
+//! [`Conversation::new`] → [`push`](Conversation::push) to add messages →
+//! [`to_api_messages`](Conversation::to_api_messages) to format for the LLM
+//! API (system prompt prepended). Persisted via [`save_conversation`](Conversation::save_conversation)
+//! and loaded via [`load_conversation`](Conversation::load_conversation).
+//! The system prompt can be hot-swapped via [`rebuild_system`](Conversation::rebuild_system).
+//!
+//! # Components
+//!
+//! - `Conversation` — message vector + session metadata + generation params
+//! - `push` / `rebuild_system` — mutation helpers
+//! - `to_api_messages` — formats messages for API consumption
+//! - `save_conversation` / `load_conversation` — filesystem persistence
 use serde::{Deserialize, Serialize};
+use tracing;
 
 use super::message::{ChatMessage, Role};
 
 /// A single conversation's message history and generation settings.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Conversation {
+    /// Ordered list of chat messages (user, assistant, tool, system).
     pub messages: Vec<ChatMessage>,
+    /// System prompt prepended at request time (see `to_api_messages`).
     pub system_prompt: String,
+    /// Foreign key referencing the owning session.
     pub session_id: String,
+    /// Model identifier string, e.g. `"anthropic/claude-opus-4-8"`.
     pub model: String,
+    /// Optional cap on output tokens.
     pub max_tokens: Option<u32>,
+    /// Optional temperature (0.0 – 2.0).
     pub temperature: Option<f32>,
 }
 
@@ -78,6 +100,7 @@ impl Conversation {
         let dir = base_dir.join("sessions").join(&self.session_id);
         std::fs::create_dir_all(&dir)?;
         let path = dir.join("conversation.json");
+        tracing::debug!(session_id = %self.session_id, path = %path.display(), "saving conversation");
         zesdex_utils::write_json_atomic(&path, self, None)?;
         Ok(())
     }
@@ -97,7 +120,8 @@ impl Conversation {
             .join("sessions")
             .join(session_id)
             .join("conversation.json");
-        let data = std::fs::read_to_string(path)?;
+        tracing::debug!(session_id = %session_id, path = %path.display(), "loading conversation");
+        let data = std::fs::read_to_string(&path)?;
         let conv: Conversation = serde_json::from_str(&data)?;
         Ok(conv)
     }