Refactor to View enum and add keybindings

Replace the `default_window` string field with a `View` enum throughout
the
application. Introduce a new keybinding module providing `Action`,
`KeyBinding` structs and helper functions, and integrate a keybindings
widget
into the main menu. Update the CLI to accept a `View` value enum and
adjust
imports and event handling accordingly. Add a release profile in
`Cargo.toml` with LTO, single codegen unit, higher optimisation level
and
binary stripping for smaller, faster builds.

src/main.rs

@@ -14,7 +14,7 @@ fn main() -> Result<()> {
     let mut terminal: Terminal<CrosstermBackend<Stdout>> = ratatui::init();
     let mut app: App = App {
         exit: false,
-        default_window: args.default_window,
+        window: args.window,
         username: args.username,
         game_mode: args.game_mode,
         map_width: args.map_width,