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

src/platform/mod.rs

@@ -1,10 +1,10 @@
 //! Platform abstraction layer for cross-platform functionality.
 
+use crate::asset::Asset;
+use crate::error::{AssetError, PlatformError};
 use std::borrow::Cow;
 use std::time::Duration;
 
-use crate::asset::{Asset, AssetError};
-
 pub mod desktop;
 pub mod emscripten;
 
@@ -30,16 +30,6 @@ pub trait Platform {
     fn get_asset_bytes(&self, asset: Asset) -> Result<Cow<'static, [u8]>, AssetError>;
 }
 
-/// Platform-specific errors.
-#[derive(Debug, thiserror::Error)]
-#[allow(dead_code)]
-pub enum PlatformError {
-    #[error("Console initialization failed: {0}")]
-    ConsoleInit(String),
-    #[error("Platform-specific error: {0}")]
-    Other(String),
-}
-
 /// Get the current platform implementation.
 #[allow(dead_code)]
 pub fn get_platform() -> &'static dyn Platform {