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/VictoryComp.ts

@@ -189,7 +189,7 @@ export class VictoryComp extends CCComp {
         if (hbNode) hbNode.active = false;
 
         // ---- 卡牌等级标识 ----
-        const cardLvStr = `lv${mvp.pool_lv || 1}`;
+        const cardLvStr = `lv${mvp.base_pool_lv || mvp.pool_lv || 1}`;
         if (lv_node) {
             lv_node.children.forEach(child => {
                 if (child.name === "light") {