refactor: 调整卡牌等级逻辑，新增基础池等级字段

1. 新增base_pool_lv字段存储英雄初始池等级
2. 替换多处直接使用pool_lv的逻辑，优先使用base_pool_lv
3. 移除预制体中废弃的pool_lv_node节点

assets/script/game/map/CardComp.ts

@@ -548,7 +548,7 @@ export class CardComp extends CCComp {
         this.isLongPressed = true;
         const heroUuid = this.card_uuid;
         const heroLv = Math.max(1, this.cardData.hero_lv ?? 1);
-        const poolLv = Math.max(1, this.cardData.pool_lv ?? 1);
+        const poolLv = Math.max(1, this.cardData.base_pool_lv ?? this.cardData.pool_lv ?? 1);
         oops.gui.remove(UIID.HInfo);
         oops.gui.open(UIID.HInfo, { heroUuid, heroLv, poolLv });
     }
@@ -607,10 +607,11 @@ export class CardComp extends CCComp {
         const kindName = CKind[this.cardData.kind];
 
         if (this.BG_node) {
+            const bgLv = this.cardData.base_pool_lv ?? this.cardData.pool_lv;
             this.BG_node.children.forEach(child => {
                 child.active = (child.name === kindName);
                 const bg = child.getComponent(CardBgComp);
-                if (bg) child.active ? bg.apply(this.cardData.pool_lv) : bg.clear();
+                if (bg) child.active ? bg.apply(bgLv) : bg.clear();
             });
         }