feat(themes): fresher store refresh + external-services notice (#1016)

* feat(themes): fresher store refresh + external-services notice

Manual refresh now fetches the registry from GitHub raw first (~5 min
cache) and falls back to the jsDelivr CDN, so a freshly merged theme shows
up without waiting on — or purging — the shared CDN @main edge (up to
12 h). Normal loads still use the CDN.

Adds a notice on the Theme Store that the catalogue and previews load from
external services (jsDelivr / GitHub), in line with the app's network
transparency. i18n ×9.

* docs(themes): note the store-refresh PR in the Theme Store entry

Now that #1015 is merged, fold PR #1016 into the still-unreleased Theme
Store changelog and credits entry.

src/locales/zh/settings.ts

@@ -322,6 +322,7 @@ export const settings = {
   themeStoreTitle: '主题商店',
   themeStoreSubmitText: '做了自己的主题？与社区分享——更多信息见主题仓库。',
   themeStoreSubmitLink: '打开主题仓库',
+  themeStoreNetworkNotice: '主题商店从外部服务（jsDelivr CDN 和 GitHub）加载目录和预览。不会发送任何个人数据。',
   themeStoreSearchPlaceholder: '搜索主题…',
   themeStoreFilterMode: '按模式筛选',
   themeStoreModeAll: '全部',