Introduces a Steam Input bridge using steamworks.js, enabling native controller support in Big Picture Mode and on Steam Deck. Adds a new steam-input-manager.js module, integrates IPC handlers in main.js, exposes a steamInputAPI in preload.js, and updates bigpicture.js to use Steam Input when available with fallback to legacy Gamepad API. Updates dependencies and scripts in package.json for Steam Deck and Big Picture profiles.
