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-ipc/src/conn.rs

@@ -9,6 +9,7 @@ use serde::de::DeserializeOwned;
 use serde::Serialize;
 use std::io::BufReader;
 use std::os::unix::net::UnixStream;
+use tracing;
 
 /// A framed JSON connection over a Unix socket.
 ///
@@ -50,6 +51,7 @@ impl Connection {
     /// [`write_frame`] for writing.
     pub fn send<T: Serialize>(&mut self, msg: &T) -> Result<()> {
         let json = serde_json::to_vec(msg).context("failed to serialise message to JSON")?;
+        tracing::trace!("sending frame ({} byte(s))", json.len());
         write_frame(&mut self.writer, &json).context("failed to write frame to connection")
     }
 
@@ -66,8 +68,12 @@ impl Connection {
         let raw = read_frame(&mut self.reader).context("failed to read frame from connection")?;
 
         match raw {
-            None => Ok(None),
+            None => {
+                tracing::trace!("connection closed (EOF)");
+                Ok(None)
+            }
             Some(bytes) => {
+                tracing::trace!("received frame ({} byte(s))", bytes.len());
                 let msg: T = serde_json::from_slice(&bytes).with_context(|| {
                     format!("failed to deserialise frame ({} byte(s))", bytes.len())
                 })?;