feat(game): 添加成都麻将打牌功能和E2E测试

- 添加discardPending状态控制丢弃牌操作
- 实现canDiscardTiles计算属性判断是否可以丢弃牌
- 新增handleRoomStateResponse函数处理房间状态响应
- 实现discardTile函数发送丢弃牌消息
- 在游戏页面添加手牌操作栏显示可丢弃的牌
- 为定缺按钮和准备按钮添加data-testid标识
- 在大厅页面为房间操作元素添加data-testid标识
- 添加手牌操作相关的CSS样式
- 配置Playwright E2E测试框架
- 创建房间流程到打牌的完整E2E测试用例

src/assets/styles/room.css

@@ -917,6 +917,43 @@
   margin-bottom: 10px;
 }
 
+.hand-action-bar {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  justify-content: center;
+  max-width: min(760px, calc(100vw - 120px));
+  margin: 0 auto;
+  padding: 10px 14px;
+  border-radius: 18px;
+  background: rgba(14, 25, 22, 0.72);
+  box-shadow: 0 10px 24px rgba(0, 0, 0, 0.24);
+}
+
+.hand-action-tile {
+  min-width: 58px;
+  padding: 10px 12px;
+  border: 1px solid rgba(255, 255, 255, 0.18);
+  border-radius: 12px;
+  background: linear-gradient(180deg, rgba(244, 228, 194, 0.98), rgba(214, 190, 145, 0.96));
+  color: #2e1e14;
+  font-size: 15px;
+  font-weight: 800;
+  letter-spacing: 0.04em;
+  box-shadow:
+    inset 0 1px 0 rgba(255, 255, 255, 0.4),
+    0 6px 14px rgba(0, 0, 0, 0.18);
+  transition: transform 120ms ease-out, box-shadow 120ms ease-out, opacity 120ms ease-out;
+}
+
+.hand-action-tile:active:not(:disabled) {
+  transform: translateY(1px);
+}
+
+.hand-action-tile:disabled {
+  opacity: 0.55;
+}
+
 .ding-que-bar {
   position: absolute;
   right: 150px;