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_lock_repo.rs

@@ -6,10 +6,23 @@
 //! check to guard against PID reuse. This repository is stateless (no
 //! `Drop`-based auto-release) — callers that need panic-safety should wrap
 //! acquisition in their own RAII guard (see `zesdex-backend`'s
-//! `main.rs::SessionLockGuard`, added in a later task of this plan).
+//! `main.rs::SessionLockGuard`).
+//!
+//! # Flow
+//!
+//! 1. **`try_lock`** — attempt `O_CREAT|O_EXCL` open on `<session_dir>/.lock`;
+//!    if it already exists, check PID liveness; if stale, overwrite atomically.
+//! 2. **`unlock`** — remove the `.lock` file.
+//! 3. **`is_alive`** — `libc::kill(pid, 0)` + `/proc/<pid>/exe` identity check.
+//!
+//! # Components
+//!
+//! - `FileSystemSessionLockRepository` — stateless singleton implementing
+//!   `SessionLockRepository`
 use std::fs;
 use std::io::Write;
 use std::path::Path;
+use tracing;
 
 use crate::domain::repository::SessionLockRepository;
 
@@ -38,17 +51,22 @@ impl SessionLockRepository for FileSystemSessionLockRepository {
             Ok(mut file) => {
                 write!(file, "{pid}")?;
                 file.sync_all()?;
+                tracing::debug!(path = %path.display(), pid, "session lock acquired");
                 return Ok(true);
             }
-            Err(ref e) if e.kind() == std::io::ErrorKind::AlreadyExists => {}
+            Err(ref e) if e.kind() == std::io::ErrorKind::AlreadyExists => {
+                tracing::debug!(path = %path.display(), "lock file exists, checking staleness");
+            }
             Err(e) => return Err(e.into()),
         }
 
         let content = fs::read_to_string(&path).unwrap_or_default();
         if let Ok(existing_pid) = content.trim().parse::<u32>() {
             if self.is_alive(existing_pid) {
+                tracing::warn!(existing_pid, path = %path.display(), "session lock held by live process");
                 return Ok(false);
             }
+            tracing::debug!(existing_pid, "stale lock detected, overwriting");
         }
 
         let tmp = path.with_extension("lock.tmp");