Refactor styles and implement new canvas viewport

- Updated styles in `styles.rs` to include new pane and canvas backgrounds, while marking unused functions with `#[allow(dead_code)]`.
- Modified `text_editor.rs` to suppress warnings for unused function parameters.
- Enhanced `title_bar.rs` to create a unified title/menu bar with improved hover states and draggable functionality.
- Simplified `sidebar.rs` to always use a single-column layout and improved tool button styling with hover feedback.
- Added a new `viewport.rs` file to implement a custom canvas viewport widget for zoom and pan rendering, replacing the previous layout-based approach.
- Updated theme management in `theme.rs` to suppress warnings for unused methods.
- Adjusted line count report to reflect recent changes in codebase.

hcie-iced-app/crates/hcie-iced-gui/src/main.rs

@@ -59,9 +59,10 @@ fn main() {
         .subscription(HcieIcedApp::subscription)
         .theme(HcieIcedApp::theme)
         .window_size((1280.0, 800.0))
+        .decorations(false)
         .run_with(move || {
-            let mut app = HcieIcedApp::new(load_path);
+            let (mut app, init_task) = HcieIcedApp::new(load_path);
             app.tablet_state = tablet_state;
-            (app, iced::Task::none())
+            (app, init_task)
         });
 }