Unify input behind Engine::Input facade; fix Ctrl+P and Pause button

New Engine/Core/Input.h/.cpp: static input facade with a Key/MouseButton
enum (values map to GLFW key codes internally) so scripts and game logic
no longer touch GLFW directly - window backend becomes swappable and the
facade is the surface to expose when embedding scripting later. Wired up
in Application's constructor; Camera (editor camera WASD/RMB/MMB), the
WASDMove script and SandboxApp key handling now query Input only.

Ctrl+P hotkey fix: the !m_Playing guard made the hotkey dead exactly
when it was needed - after pressing Play. Now toggles both ways.

Toolbar Pause button now reads "Resume" while paused (tooltip follows).

Engine/src/Core/Application.cpp

@@ -4,6 +4,7 @@
 
 #include <Engine/Core/Application.h>
 #include <Engine/Core/Window.h>
+#include <Engine/Core/Input.h>
 #include <Engine/Core/Log.h>
 #include <Engine/ECS/Scene.h>
 #include <Engine/Physics/PhysicsWorld.h>
@@ -39,6 +40,10 @@ namespace Engine {
         // 资产层不感知 Vulkan 具体类。
         // 声明在 Renderer 之后 → 析构先于 Renderer（它引用其子模块）
         m_Assets = CreateScope<Assets::AssetManager>(m_Renderer->GetAssetUploader());
+
+        // 统一输入门面装配：脚本/游戏逻辑经 Input 查询键鼠，不直接
+        // 依赖 Window 后端（GLFW 解耦）
+        Input::Init(*m_Window);
     }
 
     Application::~Application()