Initialize skirmish board and refactor states

- Create `GameStates` from a `&Cli` and initialize the skirmish board in
  `App::new`.
- Move map dimensions to `SkirmishState` and add a `board_cells` vector
  populated by `CellWidget`s.
- Refactor `SettingsState` to store only user‑specific settings (fields
  are cloned).
- Update `BoardWidget` to hold a reference to the cell vector and use
  the new dimensions.
- Adjust CLI defaults: map width to 50 and map height to 25.

src/app/app.rs

@@ -25,10 +25,13 @@ pub struct App {
 
 impl App {
     pub fn new(args: Cli) -> Self {
+        let mut states: GameStates = GameStates::new(&args);
+        states.skirmish.init_board();
+
         Self {
             exit: false,
             view: args.view,
-            states: GameStates::new(args),
+            states,
         }
     }