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/view/overlays/loading.rs

@@ -1,15 +1,24 @@
+//! Overlay: loading / processing spinner — shown during blocking operations
+//! (e.g., streaming response, tool execution).
+//!
+//! Flow: renders an animated spinner frame from `state.misc.tick_count` with
+//! a "Processing, please wait..." message.
+
 use ratatui::style::{Modifier, Style};
 use ratatui::text::Span;
 use ratatui::widgets::{Block, Paragraph};
 use ratatui::Frame;
 use crate::view::theme::Theme;
+use tracing;
 
+/// Render the Loading overlay — spinner animation + processing message.
 pub fn render(
     frame: &mut Frame,
     area: ratatui::layout::Rect,
     block: Block<'static>,
     state: &crate::app::state::rest::AppStateRest,
 ) {
+    tracing::debug!("overlay: Loading");
     let block = block
         .title(Span::styled(
             " Loading ",