feat(hero, map): 修复FlashSprite查找逻辑，新增英雄升级触发特效

优化HeroViewComp中的FlashSprite查找逻辑，统一为先查找自身节点再遍历子节点
将HeroViewComp的lv_up方法改为公有以支持外部调用
在MissionHeroComp的英雄升级流程中添加升级特效触发代码

assets/script/game/map/MissionHeroComp.ts

@@ -262,6 +262,13 @@ export class MissionHeroCompComp extends CCComp {
             model.hp_max = Math.max(1, hp_max);
             model.hp = model.hp_max;
             model.dirty_hp = true;
+
+            // 获取视图组件触发升级特效(包含描边更新)
+            const view = hero.get(HeroViewComp);
+            if (view && typeof view['lv_up'] === 'function') {
+                view['lv_up']();
+            }
+
             oops.message.dispatchEvent(GameEvent.MasterCalled, {
                 eid: hero.eid,
                 model: model