feat: 新增指定目标卡池等级抽卡功能并调整UI布局

- 在drawCardsByRule函数中增加targetPoolLv参数，支持强制从指定等级卡池抽卡
- 修改MissionCardComp中刷新英雄卡牌逻辑，使用targetPoolLv替代heroLv参数
- 调整role_controller.prefab中多个UI元素的位置和尺寸
- 将开始按钮文本从"开始"改为"开始战斗"并加宽按钮

assets/script/game/map/MissionCardComp.ts

@@ -438,12 +438,12 @@ export class MissionCardComp extends CCComp {
         return filled;
     }
 
-    private tryRefreshHeroCards(heroType?: HType, heroLv?: number): boolean {
+    private tryRefreshHeroCards(heroType?: HType, targetPoolLv?: number): boolean {
         const cards = drawCardsByRule(this.poolLv, {
             count: 4,
             type: CardType.Hero,
             heroType,
-            heroLv
+            targetPoolLv
         });
         if (cards.length <= 0) return false;
         this.layoutCardSlots();
@@ -453,8 +453,8 @@ export class MissionCardComp extends CCComp {
 
     private tryRefreshHeroCardsByEffect(refreshHeroType: SpecialRefreshHeroType, refreshLv: number): boolean {
         const heroType = this.resolveRefreshHeroType(refreshHeroType);
-        const heroLv = refreshLv > 0 ? refreshLv : undefined;
-        return this.tryRefreshHeroCards(heroType, heroLv);
+        const targetPoolLv = refreshLv > 0 ? refreshLv : undefined;
+        return this.tryRefreshHeroCards(heroType, targetPoolLv);
     }
 
     private resolveRefreshHeroType(refreshHeroType: SpecialRefreshHeroType): HType | undefined {