feat(client): add PlayerAction struct and payload types

- Introduced `PlayerAction` to encapsulate player actions, including type and payload.
- Added specific payload structures for connect, start game, play card, and draw card actions.

src/client/PlayerAction.cpp

@@ -0,0 +1,22 @@
+/**
+ * @file PlayerAction.cpp
+ *
+ * @author Yuzhe Guo
+ * @date 2025.12.07
+ */
+
+#include "PlayerAction.h"
+
+#include <stdexcept>
+
+namespace UNO::CLIENT {
+    PlayerAction::PlayerAction(PlayerActionType type, PlayerActionPayload payload) : playerActionType(type), payload(std::move(payload))
+    {
+        if (playerActionType == PlayerActionType::CONNECT && std::holds_alternative<PlayerConnectPayload>(payload) == false
+            || playerActionType == PlayerActionType::START_GAME && std::holds_alternative<PlayerStartGamePayload>(payload) == false
+            || playerActionType == PlayerActionType::PLAY_CARD && std::holds_alternative<PlayerPlayCardPayload>(payload) == false
+            || playerActionType == PlayerActionType::DRAW_CARD && std::holds_alternative<PlayerDrawCardPayload>(payload) == false) {
+            throw std::invalid_argument("Payload type do not match");
+        }
+    }
+}   // namespace UNO::CLIENT

src/client/PlayerAction.h

@@ -0,0 +1,38 @@
+/**
+ * @file PlayerAction.h
+ *
+ * @author Yuzhe Guo
+ * @date 2025.12.07
+ */
+#pragma once
+#include <string>
+#include <variant>
+
+#include "../game/Card.h"
+
+namespace UNO::CLIENT {
+    enum class PlayerActionType { CONNECT, START_GAME, PLAY_CARD, DRAW_CARD };
+
+    struct PlayerConnectPayload {
+        std::string playerName;
+        std::string host;
+        uint16_t port;
+    };
+
+    struct PlayerStartGamePayload {};
+
+    struct PlayerPlayCardPayload {
+        GAME::Card card;
+    };
+
+    struct PlayerDrawCardPayload {};
+
+    using PlayerActionPayload = std::variant<PlayerConnectPayload, PlayerStartGamePayload, PlayerPlayCardPayload, PlayerDrawCardPayload>;
+
+    struct PlayerAction {
+        PlayerActionType playerActionType;
+        PlayerActionPayload payload;
+
+        PlayerAction(PlayerActionType type, PlayerActionPayload payload);
+    };
+}   // namespace UNO::CLIENT