fix(service): 修正推荐主题查询逻辑避免重复数据

优化 getRecommendedThemes 方法，使用 limit(8) 替代 SQL 的 LIMIT 8，防止分页插件干扰，确保只返回 8 条未购买的热门主题。

src/main/java/com/yolo/keyborad/service/impl/KeyboardThemesServiceImpl.java

@@ -1,6 +1,7 @@
 package com.yolo.keyborad.service.impl;
 
 import cn.hutool.core.bean.BeanUtil;
+import com.baomidou.mybatisplus.extension.conditions.query.LambdaQueryChainWrapper;
 import com.yolo.keyborad.model.entity.KeyboardThemePurchase;
 import com.yolo.keyborad.service.KeyboardThemePurchaseService;
 import jakarta.annotation.Resource;
@@ -132,15 +133,23 @@ public class KeyboardThemesServiceImpl extends ServiceImpl<KeyboardThemesMapper,
                 .map(KeyboardThemePurchase::getThemeId)
                 .collect(Collectors.toSet());
 
-        // 查询推荐主题列表：未删除、已启用、未购买、按真实下载量降序、限制8条
-        return this.lambdaQuery()
+        // 构建查询器
+        LambdaQueryChainWrapper<KeyboardThemes> queryWrapper = this.lambdaQuery()
                 .eq(KeyboardThemes::getDeleted, false)
                 .eq(KeyboardThemes::getThemeStatus, true)
-                .notIn(!purchasedThemeIds.isEmpty(), KeyboardThemes::getId, purchasedThemeIds)
-                .orderByDesc(KeyboardThemes::getRealDownloadCount)
-                .last("LIMIT 8")
-                .list()
-                .stream()
+                .orderByDesc(KeyboardThemes::getRealDownloadCount);
+
+        // 如果有已购买的主题，排除它们
+        if (!purchasedThemeIds.isEmpty()) {
+            queryWrapper.notIn(KeyboardThemes::getId, purchasedThemeIds);
+        }
+
+        // 查询推荐主题列表，限制8条
+        List<KeyboardThemes> themesList = queryWrapper.list();
+
+        // 只取前8条数据
+        return themesList.stream()
+                .limit(8)
                 .map(theme -> {
                     KeyboardThemesRespVO vo = BeanUtil.copyProperties(theme, KeyboardThemesRespVO.class);
                     // 推荐列表中的主题均为未购买状态