Update formatting to use 4‑space indentation

- Adjust rustfmt.toml to set tab_spaces = 4.
- Reformat imports, struct definitions, function bodies, and match arms
  across the project to match the new style (aligned fields, added
  spacing, etc.).
- Ensure all code complies with the updated rustfmt settings.

src/app/widgets/board.rs

@@ -1,46 +1,45 @@
 use crate::app::states::skirmish_states::BoardState;
 use ratatui::{
-  buffer::Buffer,
-  layout::{Constraint, Layout, Rect},
-  widgets::Widget,
+    buffer::Buffer,
+    layout::{Constraint, Layout, Rect},
+    widgets::Widget,
 };
 use std::rc::Rc;
 
 pub struct BoardWidget<'a> {
-  state: &'a BoardState,
+    state: &'a BoardState,
 }
 
 impl<'a> BoardWidget<'a> {
-  pub fn new(state: &'a BoardState) -> Self {
-    Self { state }
-  }
+    pub fn new(state: &'a BoardState) -> Self {
+        Self { state }
+    }
 }
 
 impl Widget for BoardWidget<'_> {
-  fn render(self, area: Rect, buf: &mut Buffer) {
-    let horizontal: Rc<[Rect]> =
-      Layout::horizontal(vec![
-        Constraint::Length(self.state.cell_width as u16);
-        self.state.cols
-      ])
-      .split(area);
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let horizontal: Rc<[Rect]> =
+            Layout::horizontal(vec![
+                Constraint::Length(self.state.cell_width as u16);
+                self.state.cols
+            ])
+            .split(area);
 
-    for (col_idx, col_area) in horizontal.iter().enumerate() {
-      let vertical: Rc<[Rect]> =
-        Layout::vertical(vec![
-          Constraint::Length(self.state.cell_height as u16);
-          self.state.rows
-        ])
-        .split(*col_area);
+        for (col_idx, col_area) in horizontal.iter().enumerate() {
+            let vertical: Rc<[Rect]> =
+                Layout::vertical(vec![
+                    Constraint::Length(self.state.cell_height as u16);
+                    self.state.rows
+                ])
+                .split(*col_area);
 
-      for (row_idx, cell_area) in vertical.iter().enumerate() {
-        self
-          .state
-          .cells
-          .get(row_idx + self.state.vertical_offset.get_value())
-          .and_then(|rows| rows.get(col_idx + self.state.horizontal_offset.get_value()))
-          .map(|cell| cell.clone().render(*cell_area, buf));
-      }
+            for (row_idx, cell_area) in vertical.iter().enumerate() {
+                self.state
+                    .cells
+                    .get(row_idx + self.state.vertical_offset.get_value())
+                    .and_then(|rows| rows.get(col_idx + self.state.horizontal_offset.get_value()))
+                    .map(|cell| cell.clone().render(*cell_area, buf));
+            }
+        }
     }
-  }
 }