refactor(map): 抽象卡牌背景颜色逻辑，简化代码

将多个文件中重复的卡池颜色切换逻辑提取为CardBgComp组件，
减少重复代码，提高可维护性

assets/script/game/map/CardBgComp.ts

@@ -0,0 +1,18 @@
+import { _decorator, Component } from "cc";
+
+const { ccclass } = _decorator;
+
+const POOL_COLORS = ["green", "blue", "purple", "yellow", "red"];
+
+@ccclass('CardBgComp')
+export class CardBgComp extends Component {
+
+    apply(poolLv: number) {
+        const color = POOL_COLORS[Math.min(poolLv, 5) - 1];
+        this.node.children.forEach(c => c.active = c.name === color);
+    }
+
+    clear() {
+        this.node.children.forEach(c => c.active = false);
+    }
+}