phsl / new-api

This commit brings System Settings in line with Payment Settings and
prepares the whole component for multi-language deployments.

Key points
----------
• Introduced a “General Settings” card in `SystemSetting.js`
  - Adds a `ServerAddress` field (copied from Payment Settings).
  - Explains that this URL is used for payment callback & default homepage.
  - Implements `submitServerAddress` to persist the option.

• Internationalisation
  - Imported `useTranslation` and wrapped **all** Chinese UI strings in `t()`.
  - Localised section titles, labels, placeholders, banners, buttons,
    modal texts and toast messages.
  - Dynamic banner/tool-tip descriptions now combine `t()` fragments with
    template literals for runtime URLs.

• UX improvements
  - Added contextual `extraText` under the ServerAddress input.
  - Ensured placeholders like “sensitive info…” are translatable.

With these changes, administrators can configure the server URL from the
System Settings tab, and the entire page is ready for seamless language
switching via the existing i18n framework.