Add Settings view, widget, and keybindings

Introduce Settings view handling in key events and widgets.
Add `Enter` action with its keybinding.
Refactor keybinding lookup to use `Option<&KeyBinding>` for missing
entries.
Update view option generation to safely filter possible values.
Export `settings_keybindings` and `settings_widget` from their modules.

src/app/widgets/keybindings.rs

@@ -26,9 +26,15 @@ impl KeybindingsWidget {
 
             let grouped_lines: Vec<Line<'_>> = keybindings
                 .iter()
-                .filter(|b| b.group == group)
-                .map(|b| {
-                    Line::from_iter([b.symbol.red().bold(), " - ".into(), b.description.into()])
+                .filter(|b| b.as_ref().map_or(false, |kb| kb.group == group))
+                .filter_map(|b| {
+                    b.as_ref().map(|kb| {
+                        Line::from_iter([
+                            kb.symbol.red().bold(),
+                            " - ".into(),
+                            kb.description.into(),
+                        ])
+                    })
                 })
                 .collect();
 

src/app/widgets/main_menu.rs

@@ -12,15 +12,15 @@ fn view_options() -> Vec<(usize, String)> {
     View::value_variants()
         .iter()
         .enumerate()
-        .map(|(i, v)| {
-            let name = v
-                .to_possible_value()
-                .unwrap()
-                .get_name()
-                .replace('-', " ")
-                .to_uppercase()
-                .to_string();
-            (i, name)
+        .filter_map(|(i, v)| {
+            v.to_possible_value().map(|possible_value| {
+                let name = possible_value
+                    .get_name()
+                    .replace('-', " ")
+                    .to_uppercase()
+                    .to_string();
+                (i, name)
+            })
         })
         .filter(|(_, v)| v != "MAIN MENU")
         .collect()

src/app/widgets/mod.rs

@@ -1,7 +1,9 @@
 pub mod default;
 pub mod keybindings;
 pub mod main_menu;
+pub mod settings;
 
 pub use default::default_view_widget;
 pub use keybindings::KeybindingsWidget;
 pub use main_menu::main_menu_widget;
+pub use settings::settings_widget;

src/app/widgets/settings.rs

@@ -0,0 +1,41 @@
+use crate::app::{App, widgets::KeybindingsWidget};
+use ratatui::{
+    buffer::Buffer,
+    layout::{Alignment, Constraint, Layout, Rect},
+    style::Stylize,
+    widgets::{Block, Borders, Padding, Paragraph, Widget},
+};
+
+pub fn settings_widget(app: &App, area: Rect, buf: &mut Buffer) {
+    let vertical_layout: Layout = Layout::vertical([
+        Constraint::Length(10),
+        Constraint::Fill(1),
+        Constraint::Length(4),
+    ]);
+
+    let [title_area, main_area, keybindings_area] = vertical_layout.areas(area);
+
+    Paragraph::new("War in tunnels")
+        .alignment(Alignment::Left)
+        .yellow()
+        .block(
+            Block::new()
+                .gray()
+                .borders(Borders::LEFT | Borders::TOP | Borders::RIGHT)
+                .padding(Padding::new(1, 1, 1, 1)),
+        )
+        .render(title_area, buf);
+
+    Paragraph::new("Settings")
+        .alignment(Alignment::Center)
+        .yellow()
+        .block(
+            Block::new()
+                .gray()
+                .borders(Borders::LEFT | Borders::RIGHT)
+                .padding(Padding::new(1, 1, 1, 1)),
+        )
+        .render(main_area, buf);
+
+    KeybindingsWidget::new(app.view).render(keybindings_area, buf);
+}