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/store.rs

@@ -1,6 +1,18 @@
 //! Filesystem layout for zesdex's persistent and scratch data directories.
+//!
+//! # Flow
+//!
+//! [`Store::new`] resolves all paths from OS data dir / temp dir →
+//! [`ensure_dirs`](Store::ensure_dirs) creates them on startup.
+//!
+//! # Components
+//!
+//! - `Store` — resolved path bundle (base, memory, scratch, images, downloads)
+//! - `new` — path computation (no I/O)
+//! - `ensure_dirs` — creates all directories if missing
 use serde::{Deserialize, Serialize};
 use std::path::PathBuf;
+use tracing;
 
 /// Resolved paths for all data directories zesdex reads from and writes to.
 ///
@@ -8,10 +20,15 @@ use std::path::PathBuf;
 /// where memory, scratch, session images, and downloads live.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Store {
+    /// Top-level data directory, e.g. `~/.local/share/zesdex`.
     pub base_dir: PathBuf,
+    /// Temporary scratch root, usually under the OS temp dir.
     pub scratch_root: PathBuf,
+    /// Directory for persistent memory files (`.md` summaries).
     pub memory_dir: PathBuf,
+    /// Directory for per-session image snapshots.
     pub session_images_dir: PathBuf,
+    /// Directory for downloaded files.
     pub download_dir: PathBuf,
 }
 
@@ -41,6 +58,7 @@ impl Store {
     ///
     /// Return: `Err` on the first directory that fails to create.
     pub fn ensure_dirs(&self) -> std::io::Result<()> {
+        tracing::debug!(base = %self.base_dir.display(), "ensuring store directories exist");
         std::fs::create_dir_all(&self.base_dir)?;
         std::fs::create_dir_all(&self.memory_dir)?;
         std::fs::create_dir_all(&self.scratch_root)?;