Section 04 "Notification display" holds a single select populated from a
frozen catalogue of the 16 zones the server accepts, with Asia/Shanghai
selected by default. Labels are per-zone (`label.en` / `label.zh`) so they
follow the existing browser-language switch.
readBusinessConfig now submits the selection under the `timezone` key.
- detect locale from navigator.language (zh* -> zh, otherwise en) at startup;
<html lang> switches accordingly; English is the default
- index.html carries English default text plus data-i18n /
data-i18n-placeholder / data-i18n-aria attributes
- config.js holds inline en/zh dictionaries, t(key, vars) and detectLocale();
dynamic Chinese strings become t() calls with {var} interpolation
- no new asset files (src/web.rs serves only config.js and styles.css);
stays a build-less vanilla-JS single page
- config.test.mjs updated to the English defaults; adds dictionary key-parity
and markup key-coverage tests
anonsaber