fix(整合): 修复更新日志模态框层级被其他元素遮挡的问题

- 将模态框背景遮罩 z-index 从 z-50 提升到 z-[100]
- 将模态框内容 z-index 从 z-50 提升到 z-[101]
- 确保模态框在所有其他元素（Header 搜索、Sidebar、全屏矩阵等）之上显示

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <noreply@hapi.run>

src/data/changelog.json

@@ -1,5 +1,12 @@
 {
   "changelogEntries": [
+    {
+      "id": "2026-03-08-fix-modal-zindex",
+      "date": "2026-03-08",
+      "type": "fix",
+      "title": "修复更新日志模态框层级被其他元素遮挡的问题",
+      "scope": "整合"
+    },
     {
       "id": "2026-03-08-update-changelog-rule",
       "date": "2026-03-08",