refractor(game): enhance state management with clear and endGame methods

- Added `clear` methods to `PlayerState`, `ServerPlayerState`, and `HandCard`.
- Introduced `endGame` methods to `GameState`, `ClientGameState`, and `ServerGameState`.
- Improved `init` and `nextPlayer` logic in `ClientGameState`.
- Added `getClientGameStage` and `getServerGameStage` methods to retrieve game stages.

src/game/Player.h

@@ -59,6 +59,11 @@ namespace UNO::GAME {
          * @return 手牌是否为空
          */
         [[nodiscard]] bool isEmpty() const;
+
+        /**
+         * 清空手牌
+         */
+        void clear();
     };
 
     /**
@@ -105,6 +110,11 @@ namespace UNO::GAME {
          * @return 手牌是否为空
          */
         [[nodiscard]] bool isEmpty() const;
+
+        /**
+         * 清空手牌
+         */
+        void clear();
     };
 }   // namespace UNO::GAME