feat(analytics): 数据分析页增加访问与受控设备的国家维度分布

参考受控版本分布的饼图实现，新增国家维度分布：
- AnalyticsDailyDim 增加 KIND_VISIT_COUNTRY / KIND_DEVICE_COUNTRY 常量
- AnalyticsReportService::aggregateDay() 按 country 聚合访问 UV 与受控设备数
- present() 汇总并返回 by_visit_country / by_device_country（ISO 代码转中文名展示）
- 视图新增两个国家饼图卡片与两个国家明细标签区

性能与正确性修复：
- ensureCached() 改为一次查询校验所有按日聚合 kind 的缓存完整性，
  避免旧缓存完整时新维度不被聚合的问题
- 新增迁移为 page_visits / devices 建立 (created_at, country) 复合索引，
  对齐 os_version 维度的索引做法，加速按日期范围 + GROUP BY country 的聚合

resources/views/admin/reports/analytics.blade.php

@@ -146,6 +146,27 @@
   </div>
 </div>
 
+<div class="layui-row layui-col-space15">
+  <div class="layui-col-md6">
+    <div class="layui-card an-pie-card">
+      <div class="layui-card-header">访问 · 国家</div>
+      <div class="layui-card-body">
+        <div id="an-visit-country-chart" class="an-pie"></div>
+        <p class="an-pie-hint" id="an-visit-country-hint"></p>
+      </div>
+    </div>
+  </div>
+  <div class="layui-col-md6">
+    <div class="layui-card an-pie-card">
+      <div class="layui-card-header">受控设备 · 国家</div>
+      <div class="layui-card-body">
+        <div id="an-device-country-chart" class="an-pie"></div>
+        <p class="an-pie-hint" id="an-device-country-hint"></p>
+      </div>
+    </div>
+  </div>
+</div>
+
 <div class="layui-card">
   <div class="layui-card-header">受控设备版本明细 <span class="layui-word-aux" id="an-device-count"></span></div>
   <div class="layui-card-body">
@@ -158,6 +179,18 @@
     <div class="an-tags" id="an-by-ios-version"><span class="an-tags-empty">—</span></div>
   </div>
 </div>
+<div class="layui-card">
+  <div class="layui-card-header">访问国家明细 <span class="layui-word-aux" id="an-visit-country-count"></span></div>
+  <div class="layui-card-body">
+    <div class="an-tags" id="an-by-visit-country"><span class="an-tags-empty">—</span></div>
+  </div>
+</div>
+<div class="layui-card">
+  <div class="layui-card-header">受控设备国家明细 <span class="layui-word-aux" id="an-device-country-count"></span></div>
+  <div class="layui-card-body">
+    <div class="an-tags" id="an-by-device-country"><span class="an-tags-empty">—</span></div>
+  </div>
+</div>
 <div class="layui-word-aux" id="an-range" style="margin:0 0 12px;"></div>
 @endsection
 
@@ -340,12 +373,20 @@ layui.use(['form', 'laydate', 'layer', 'echarts'], function () {
     renderPie('an-os-chart', 'an-os-hint', data.by_os, 'uv', '系统');
     renderPie('an-ios-chart', 'an-ios-hint', data.by_ios_version, 'uv', 'iOS 版本');
     renderPie('an-device-chart', 'an-device-hint', data.by_device_ios_version, 'count', '受控版本');
+    renderPie('an-visit-country-chart', 'an-visit-country-hint', data.by_visit_country, 'uv', '访问国家');
+    renderPie('an-device-country-chart', 'an-device-country-hint', data.by_device_country, 'count', '受控国家');
     fillTags('#an-by-ios-version', data.by_ios_version, 'uv');
     fillTags('#an-by-device-ios', data.by_device_ios_version, 'count');
+    fillTags('#an-by-visit-country', data.by_visit_country, 'uv');
+    fillTags('#an-by-device-country', data.by_device_country, 'count');
     var iosN = (data.by_ios_version || []).length;
     var deviceN = (data.by_device_ios_version || []).length;
+    var visitCountryN = (data.by_visit_country || []).length;
+    var deviceCountryN = (data.by_device_country || []).length;
     $('#an-ios-count').text(iosN ? ('· ' + iosN + ' 个') : '');
     $('#an-device-count').text(deviceN ? ('· ' + deviceN + ' 个') : '');
+    $('#an-visit-country-count').text(visitCountryN ? ('· ' + visitCountryN + ' 个') : '');
+    $('#an-device-country-count').text(deviceCountryN ? ('· ' + deviceCountryN + ' 个') : '');
     var computed = data.computed_at ? (' · 汇总于 ' + data.computed_at) : '';
     $('#an-range').text('统计区间：' + data.from + ' ~ ' + data.to + '（按日去重后加总，今日约 15 分钟刷新）' + computed);
   }