feat(stats): consolidate per-user sync status into the Stats page

The Settings > Sync tab moves into the Stats module: Stats is now a per-user
page (Overview tab = sync status + your own API usage + manual actions) with the
admin instance-wide quota dashboard + background-sync pause as an admin-only
System tab. The Stats nav item is visible to all users (was admin-only); the
Settings Sync tab is removed. Sync i18n strings move from settings.sync.* to
stats.sync.* (EN/HU/DE).

frontend/src/App.tsx

@@ -465,8 +465,8 @@ export default function App() {
                 notify({ level: "info", message: t("channels.notify.filteredByTag", { name }) });
               }}
             />
-          ) : page === "stats" && meQuery.data!.role === "admin" ? (
-            <Stats />
+          ) : page === "stats" ? (
+            <Stats me={meQuery.data!} />
           ) : page === "scheduler" && meQuery.data!.role === "admin" ? (
             <Scheduler />
           ) : page === "playlists" ? (