Introduce input modes and Pause Menu (#8)

- Add input mode switching to the Input Manager
- Automatically set input mode on scene load - UI for MainMenu and GameAndUI for other scenes
- Add PauseMenu prefab, auto-loaded via the boostrap system
- Automatically control PauseMenu visibility based on current scene

Co-authored-by: AlexanderT <alexander@foolhardyhorizons.com>
Co-authored-by: Michal Pikulski <michal.a.pikulski@gmail.com>
Reviewed-on: #8

Assets/Scripts/LevelS/LevelSwitch.cs

@@ -96,6 +96,9 @@ public class LevelSwitch : MonoBehaviour
         // Setup menu with data and callbacks
         menu.Setup(switchData, OnMenuConfirm, OnMenuCancel);
         _isActive = false; // Prevent re-triggering until menu is closed
+        
+        // Switch input mode to UI only
+        InputManager.Instance.SetInputMode(InputMode.UI);
     }
 
     private async void OnMenuConfirm()