[WINDOW] Implement Input polling class

[mrgreenapple24]

Goal

Static Input class for polling key/mouse state each frame, independent of the event system.

Tasks

• Input class with static methods:
  • IsKeyPressed(KeyCode) -> bool
  • IsMouseButtonPressed(MouseCode) -> bool
  • GetMouseX() -> float, GetMouseY() -> float
  • GetMousePosition() -> std::pair<float,float>
• Define KeyCode and MouseCode enums mapping to GLFW key/button codes
• Implement using glfwGetKey / glfwGetMouseButton / glfwGetCursorPos on the native window
• Provide platform-specific implementations behind the interface pattern

Acceptance Criteria

Input::IsKeyPressed(Key::Space) returns true only while Space is held.