refactor: restructure game logic and state management into separate modules

- Moved game logic from `game.rs` to `game/mod.rs` and `game/state.rs` for better organization.
- Updated `App` to utilize the new `Game` struct and its state management.
- Refactored error handling
- Removed unused audio subsystem references

tests/game.rs

@@ -10,15 +10,4 @@ fn test_game_map_creation() {
 
     assert!(map.graph.node_count() > 0);
     assert!(!map.grid_to_node.is_empty());
-
-    // Should find Pac-Man's starting position
-    let pacman_pos = map.find_starting_position(0);
-    assert!(pacman_pos.is_some());
-}
-
-#[test]
-fn test_game_score_initialization() {
-    // This would require creating a full Game instance, but we can test the concept
-    let map = Map::new(RAW_BOARD).unwrap();
-    assert!(map.find_starting_position(0).is_some());
 }