Add scrolling actions and board widget

Introduce directional and scroll actions, update keybindings, add
scrollbar
state to SkirmishState, and render the board with a new BoardWidget.
Adjust CLI
defaults and layout heights accordingly.

src/app/widgets/cell.rs

@@ -0,0 +1,35 @@
+use ratatui::{
+    buffer::Buffer,
+    layout::{Alignment, Rect},
+    style::Stylize,
+    widgets::{Block, Borders, Paragraph, Widget},
+};
+
+// pub enum CellTags {
+//     Player,
+//     Enemy,
+//     Dirt,
+//     Tunnel,
+//     Base,
+// }
+
+pub struct CellWidget {
+    pub row: usize,
+    pub col: usize,
+    // pub tags: Vec<CellTags>,
+}
+
+impl CellWidget {
+    pub fn new(row: usize, col: usize) -> Self {
+        Self { row, col }
+    }
+}
+
+impl Widget for CellWidget {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Paragraph::new(format!("{}/{}", self.row, self.col))
+            .alignment(Alignment::Center)
+            .block(Block::default().borders(Borders::ALL).white())
+            .render(area, buf);
+    }
+}