feat: add Google Analytics (GA4) configuration (#11739)

* fix: resolve CF Worker Date.now() returning 0 at module level

In Cloudflare Workers, module-level Date.now() evaluates to 0 during
initialization, causing all time-dependent data (visitData dates,
offlineChartData times, activities updatedAt) to render as epoch-zero
values (1970-01-01, 0:00). This broke the analysis dashboard charts
on the preview site.

Convert static module-level data exports to functions that generate
data at request time, ensuring Date.now() returns the current time.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* feat: add Google Analytics (GA4) configuration

Add ga_v2 tracking ID G-59NF1VHHPF via Umi Max analytics plugin.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

config/config.ts

@@ -173,6 +173,14 @@ export default defineConfig({
    * @doc https://umijs.org/docs/max/access
    */
   access: {},
+  /**
+   * @name Google Analytics
+   * @description 使用 GA4 (gtag.js) 进行站点分析
+   * @doc https://umijs.org/docs/max/analytics
+   */
+  analytics: {
+    ga_v2: 'G-59NF1VHHPF',
+  },
   /**
    * @name <head> 中额外的 script
    * @description 配置 <head> 中额外的 script