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/infrastructure/persistence/session_repo.rs

@@ -2,7 +2,25 @@
 //!
 //! Each session is stored as `<base_dir>/sessions/<id>/session.json`.
 //! Writes use a write-then-rename + fsync pattern for crash safety.
+//!
+//! # Flow
+//!
+//! - **`list_sessions`** — enumerate `<base_dir>/sessions/` subdirectories,
+//!   attempt `load_session` on each (silently skipping failures).
+//! - **`load_session`** — validates id (path-traversal check), reads JSON.
+//! - **`save_session`** — creates session directory, writes JSON atomically.
+//! - **`delete_session`** — validates id, removes the session directory.
+//!
+//! # Security
+//!
+//! All methods that accept a user-supplied `id` string reject ids containing
+//! `/`, `\\`, or `..` to prevent directory-traversal attacks.
+//!
+//! # Components
+//!
+//! - `FileSystemSessionRepository` — stateless singleton implementing `SessionRepository`
 use std::path::Path;
+use tracing;
 
 use zesdex_utils::write_json_atomic;
 
@@ -24,6 +42,7 @@ impl SessionRepository for FileSystemSessionRepository {
     fn list_sessions(&self, base_dir: &Path) -> anyhow::Result<Vec<Session>> {
         let sessions_dir = base_dir.join("sessions");
         let Ok(entries) = std::fs::read_dir(&sessions_dir) else {
+            tracing::warn!(path = %sessions_dir.display(), "sessions directory not found");
             return Ok(Vec::new());
         };
         let mut sessions = Vec::new();
@@ -36,6 +55,7 @@ impl SessionRepository for FileSystemSessionRepository {
                 sessions.push(session);
             }
         }
+        tracing::debug!(count = sessions.len(), "listed sessions");
         Ok(sessions)
     }
 
@@ -48,6 +68,7 @@ impl SessionRepository for FileSystemSessionRepository {
         if !path.exists() {
             anyhow::bail!("session not found: {id}");
         }
+        tracing::debug!(session_id = %id, path = %path.display(), "loading session");
         let data = std::fs::read_to_string(&path)?;
         let session: Session = serde_json::from_str(&data)?;
         Ok(session)
@@ -57,6 +78,7 @@ impl SessionRepository for FileSystemSessionRepository {
         let dir = session.session_dir(base_dir);
         std::fs::create_dir_all(&dir)?;
         let path = dir.join("session.json");
+        tracing::debug!(session_id = %session.id, path = %path.display(), "saving session");
         write_json_atomic(&path, session, None)?;
         Ok(())
     }
@@ -66,6 +88,7 @@ impl SessionRepository for FileSystemSessionRepository {
             anyhow::bail!("invalid session id '{id}': must not contain path separators");
         }
         let dir = base_dir.join("sessions").join(id);
+        tracing::debug!(session_id = %id, path = %dir.display(), "deleting session");
         if dir.exists() {
             std::fs::remove_dir_all(&dir)?;
         }