GitLab

Embedded pages (purchase subscription, custom pages) now receive the
current user locale through a `lang` URL parameter, allowing iframe
content to match the user's language preference.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The backdrop-blur background on the iframe "open in new tab" floating
button was hardcoded to bg-white/80, making it look broken in dark
theme. Added dark:bg-dark-800/80 variant for both PurchaseSubscription
and CustomPage views.

Add configurable custom menu items that appear in sidebar, each rendering
an iframe-embedded external page. Includes shared URL builder with
src_host/src_url tracking, CSP frame-src multi-origin deduplication,
admin settings UI, and i18n support.

chore: bump version to 0.1.87.19
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- 新增 /purchase 页面（iframe + 新窗口兜底）

- 管理员系统设置可配置开关与URL

- 非 simple mode 才在侧边栏展示入口