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-backend/src/model/msglog/blobs.rs

@@ -8,6 +8,9 @@ use rusqlite::{params, Connection};
 /// Flow: compute current timestamp -> `INSERT OR REPLACE` into `blobs`
 /// keyed on `(session_id, blob_key)`.
 ///
+/// `INSERT OR REPLACE` is used so re-uploading the same key overwrites
+/// the previous blob rather than failing on the UNIQUE constraint.
+///
 /// Return: `Ok(())` on success, or the underlying `SQLite` error.
 pub fn store_blob(
     conn: &Connection,
@@ -17,10 +20,12 @@ pub fn store_blob(
     mime_type: Option<&str>,
 ) -> Result<()> {
     let created_at = chrono::Utc::now().timestamp_millis();
+    tracing::debug!(%session_id, %blob_key, size = data.len(), "store_blob");
     conn.execute(
         "INSERT OR REPLACE INTO blobs (session_id, blob_key, data, mime_type, created_at) VALUES (?1, ?2, ?3, ?4, ?5)",
         params![session_id, blob_key, data, mime_type, created_at],
     )?;
+    tracing::info!(%session_id, %blob_key, "store_blob — stored");
     Ok(())
 }
 
@@ -33,15 +38,25 @@ pub fn retrieve_blob(
     session_id: &str,
     blob_key: &str,
 ) -> Result<Option<Vec<u8>>> {
+    tracing::debug!(%session_id, %blob_key, "retrieve_blob");
     let result = conn.query_row(
         "SELECT data FROM blobs WHERE session_id = ?1 AND blob_key = ?2",
         params![session_id, blob_key],
-        |row| row.get(0),
+        |row| row.get::<_, Vec<u8>>(0),
     );
     match result {
-        Ok(data) => Ok(Some(data)),
-        Err(rusqlite::Error::QueryReturnedNoRows) => Ok(None),
-        Err(e) => Err(e.into()),
+        Ok(data) => {
+            tracing::debug!(%session_id, %blob_key, size = data.len(), "retrieve_blob — found");
+            Ok(Some(data))
+        }
+        Err(rusqlite::Error::QueryReturnedNoRows) => {
+            tracing::debug!(%session_id, %blob_key, "retrieve_blob — not found");
+            Ok(None)
+        }
+        Err(e) => {
+            tracing::error!(%session_id, %blob_key, error = %e, "retrieve_blob — query failed");
+            Err(e.into())
+        }
     }
 }
 
@@ -50,6 +65,7 @@ pub fn retrieve_blob(
 /// Return: `Ok(Vec<String>)` of keys ordered by `created_at`, or the
 /// underlying `SQLite` error.
 pub fn list_blob_keys(conn: &Connection, session_id: &str) -> Result<Vec<String>> {
+    tracing::debug!(%session_id, "list_blob_keys");
     let mut stmt =
         conn.prepare("SELECT blob_key FROM blobs WHERE session_id = ?1 ORDER BY created_at ASC")?;
     let rows = stmt.query_map(params![session_id], |row| row.get::<_, String>(0))?;
@@ -57,5 +73,6 @@ pub fn list_blob_keys(conn: &Connection, session_id: &str) -> Result<Vec<String>
     for row in rows {
         keys.push(row?);
     }
+    tracing::debug!(%session_id, count = keys.len(), "list_blob_keys — done");
     Ok(keys)
 }