Refactor keybinding handling and update widgets

- Remove the old `keybindings.rs` and stop re‑exporting its symbols.
- Add view‑specific handling: `App::handle_key_event` now delegates to
  `main_menu_keybindings` when the view is `MainMenu`.
- Update imports in `app.rs`, `widget.rs`, and widget modules to use the
  new `app::keybindings` path.
- Enhance `keybindings_widget` to display ↑, ↓ and “Space” for special
  keys.
- Change main menu layout percentages from 90/10 to 87/13.
- Reorder the `clap` import in `cli.rs` for consistency.

src/app/widgets/main_menu.rs

@@ -1,3 +1,4 @@
+use crate::app::{View, widgets::keybindings_widget};
 use ratatui::{
     buffer::Buffer,
     layout::{Alignment, Constraint, Layout, Rect},
@@ -5,11 +6,9 @@ use ratatui::{
     widgets::{Block, Borders, Paragraph, Widget},
 };
 
-use crate::app::{View, widgets::keybindings_widget};
-
 pub fn main_menu_widget(area: Rect, buf: &mut Buffer) {
     let vertical_layout: Layout =
-        Layout::vertical([Constraint::Percentage(90), Constraint::Percentage(10)]);
+        Layout::vertical([Constraint::Percentage(87), Constraint::Percentage(13)]);
 
     let [main_menu_area, keybindings_area] = vertical_layout.areas(area);