Drop crossterm delete App add CLI defaults

Remove the crossterm dependency and its input handling, delete the
now‑unused
App module, and provide default values for all command‑line options.

Cargo.lock

@@ -1521,7 +1521,6 @@ name = "war_in_tunnels"
 version = "0.1.0"
 dependencies = [
  "clap",
- "crossterm",
  "ratatui",
 ]