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/components/settings/ThemeStoreSection.tsx

@@ -159,6 +159,11 @@ export function ThemeStoreSection() {
         </button>
       </div>
 
+      {/* Network disclosure — the store reaches external services. */}
+      <p style={{ fontSize: 12, color: 'var(--text-muted)', margin: '0 0 1rem', lineHeight: 1.5 }}>
+        {t('settings.themeStoreNetworkNotice')}
+      </p>
+
       {/* Toolbar: search + mode filter + refresh. Hidden when offline with no
           catalogue to browse — the offline banner below stands in for it. */}
       {!error && (