feat: 实现麻将游戏结算系统与自摸胡功能

新增结算类型枚举和分数变更记录模型
补全响应裁决器与结算服务，支持点炮胡、自摸胡和明杠结算
扩展座位模型，增加已胡状态和分数字段
完善胡牌评估器，支持自摸胡判断
前端原型页增加分数显示和已胡状态
更新SPRINT文档记录当前进度

backend/src/test/java/com/xuezhanmaster/game/event/GameEventTest.java

@@ -1,7 +1,13 @@
 package com.xuezhanmaster.game.event;
 
+import com.xuezhanmaster.game.domain.ActionType;
+import com.xuezhanmaster.game.domain.ScoreChange;
+import com.xuezhanmaster.game.domain.SettlementResult;
+import com.xuezhanmaster.game.domain.SettlementType;
 import org.junit.jupiter.api.Test;
 
+import java.util.List;
+
 import static org.assertj.core.api.Assertions.assertThat;
 
 class GameEventTest {
@@ -39,4 +45,53 @@ class GameEventTest {
         assertThat(switched.eventType()).isEqualTo(GameEventType.TURN_SWITCHED);
         assertThat(switched.payload()).containsEntry("currentSeatNo", 3);
     }
+
+    @Test
+    void shouldBuildSettlementEvents() {
+        SettlementResult settlementResult = new SettlementResult(
+                SettlementType.DIAN_PAO_HU,
+                ActionType.HU,
+                2,
+                0,
+                "9筒",
+                List.of(
+                        new ScoreChange(2, 1, 3),
+                        new ScoreChange(0, -1, -2)
+                )
+        );
+
+        GameEvent settlementApplied = GameEvent.settlementApplied("game-1", settlementResult);
+        GameEvent scoreChanged = GameEvent.scoreChanged("game-1", 2, SettlementType.DIAN_PAO_HU.name(), 1, 3);
+
+        assertThat(settlementApplied.eventType()).isEqualTo(GameEventType.SETTLEMENT_APPLIED);
+        assertThat(settlementApplied.payload())
+                .containsEntry("settlementType", "DIAN_PAO_HU")
+                .containsEntry("actionType", "HU")
+                .containsEntry("sourceSeatNo", 0)
+                .containsEntry("triggerTile", "9筒");
+        assertThat(settlementApplied.payload()).containsKey("scoreChanges");
+
+        assertThat(scoreChanged.eventType()).isEqualTo(GameEventType.SCORE_CHANGED);
+        assertThat(scoreChanged.payload())
+                .containsEntry("settlementType", "DIAN_PAO_HU")
+                .containsEntry("delta", 1)
+                .containsEntry("score", 3);
+    }
+
+    @Test
+    void shouldAllowHuEventWithoutSourceSeatForSelfDraw() {
+        GameEvent selfDrawHu = GameEvent.responseActionDeclared(
+                "game-1",
+                GameEventType.HU_DECLARED,
+                0,
+                null,
+                null
+        );
+
+        assertThat(selfDrawHu.eventType()).isEqualTo(GameEventType.HU_DECLARED);
+        assertThat(selfDrawHu.payload())
+                .containsEntry("actionType", "HU")
+                .doesNotContainKey("sourceSeatNo")
+                .doesNotContainKey("tile");
+    }
 }