feat(artist): functional Artist detail screen (§A3)

Replace the scaffold Placeholder with a real artist page wired to the
existing `/artists/{id}` (+ `/albums`, `/tracks`) endpoints: header with
procedural avatar / counts / "Play all" (queues with source=artist),
discography grid (cards → album detail), and the full track list. All
three list states per async section.

Also make the Library artists-tab rows clickable → `/artists/:id`,
closing the previous navigation dead-end.

i18n: new `artist.*` block (en + ru).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/features/library/LibraryPage.tsx

@@ -216,7 +216,11 @@ export function LibraryPage() {
             {artistsQuery.data && (
               <div style={{ padding: '0.5rem 0' }}>
                 {artistsQuery.data.items.map((artist) => (
-                  <ArtistRow key={artist.id} artist={artist} />
+                  <ArtistRow
+                    key={artist.id}
+                    artist={artist}
+                    onClick={() => void navigate(`/artists/${artist.id}`)}
+                  />
                 ))}
               </div>
             )}
@@ -302,15 +306,23 @@ function AlbumCard({ album, onClick }: { album: Album; onClick: () => void }) {
   );
 }
 
-function ArtistRow({ artist }: { artist: Artist }) {
+function ArtistRow({
+  artist,
+  onClick,
+}: {
+  artist: Artist;
+  onClick: () => void;
+}) {
   const { t } = useTranslation();
   return (
     <div
+      onClick={onClick}
       style={{
         display: 'flex',
         alignItems: 'center',
         gap: '0.75rem',
         padding: '0.5rem 1.5rem',
+        cursor: 'pointer',
       }}
     >
       <div