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/nl/settings.ts

@@ -323,6 +323,7 @@ export const settings = {
   themeStoreTitle: 'Themawinkel',
   themeStoreSubmitText: 'Eigen thema gemaakt? Deel het met de community — meer info in de themarepository.',
   themeStoreSubmitLink: 'Themarepository openen',
+  themeStoreNetworkNotice: 'De Theme Store laadt de catalogus en previews van externe diensten (de jsDelivr-CDN en GitHub). Er worden geen persoonlijke gegevens verzonden.',
   themeStoreSearchPlaceholder: "Thema's zoeken…",
   themeStoreFilterMode: 'Filteren op modus',
   themeStoreModeAll: 'Alle',