[Add] End game, Restart, Final Check

Assets/Runtime/ECS/BoardEcsSyncService.cs

@@ -7,6 +7,16 @@ namespace Minesweeper.ECS
 {
     public sealed class BoardEcsSyncService : IBoardEcsSyncService
     {
+        public void ClearBoard()
+        {
+            if (!TryGetEntityManager(out var entityManager))
+            {
+                return;
+            }
+
+            ClearCells(entityManager);
+        }
+
         public void SyncBoard(IBoardService boardService)
         {
             if (!TryGetEntityManager(out var entityManager))

Assets/Runtime/ECS/IBoardEcsSyncService.cs

@@ -4,6 +4,7 @@ namespace Minesweeper.ECS
 {
     public interface IBoardEcsSyncService
     {
+        void ClearBoard();
         void SyncBoard(IBoardService boardService);
         void SyncGameState(GameState state, bool hasFirstClick);
     }