refactor(themes): drop unreliable popularity/download stats from the store (#1050)

The install/download numbers came from jsDelivr CDN hits, which are
structurally unreliable: the stats API caps at the top 100 files, so most
themes report 0 and the figures jump from day to day. Showing them — and a
popularity bar and a most-popular sort built on them — only misled users.

Remove the stats meta box (popularity bar + download count), move the author
back under the theme name, and keep the reliable git-based last-changed date
inline. Sort is now Newest (default) or Alphabetical.

src/locales/en/settings.ts

@@ -400,7 +400,7 @@ export const settings = {
   themeStoreSubmitText: 'Made your own theme? Share it with the community — more info in the themes repository.',
   themeStoreSubmitLink: 'Open the themes repository',
   themeStoreNetworkNotice: 'The Theme Store loads its catalogue and previews from external services (the jsDelivr CDN and GitHub). No personal data is sent.',
-  themeStoreStatsNotice: 'Download and last-changed stats refresh once a day (around 04:17 UTC).',
+  themeStoreStatsNotice: 'Last-changed dates refresh once a day (around 04:17 UTC).',
   themeStoreSearchPlaceholder: 'Search themes…',
   themeStoreFilterMode: 'Filter by mode',
   themeStoreModeAll: 'All',
@@ -414,12 +414,9 @@ export const settings = {
   themeStoreEmpty: 'No themes match your filters.',
   themeStoreActive: 'Active',
   themeStoreEnlarge: 'Enlarge preview',
-  themeStoreSortPopular: 'Most popular',
   themeStoreSortNewest: 'Newest',
   themeStoreSortName: 'Alphabetical',
-  themeStoreAuthor: 'Author',
-  themeStorePopularity: 'Popularity',
-  themeStoreDownloads: 'Total downloads',
+  themeStoreByAuthor: 'by {{author}}',
   themeStoreLastChanged: 'Last changed',
   themeMigrationNoticeTitle: 'Theme moved to the Store',
   themeMigrationNoticeBody: '{{themes}} is no longer bundled with the app. You can reinstall it from the Theme Store (Settings → Themes), or pick another theme.',