feat: full artist release list via artist/getReleasesList

Instead of relying on the limited preview in artist/page, fire a
separate artist/getReleasesList request per release type (album,
epSingle, live, compilation) in parallel when loading an artist.
Each result updates its section independently as it arrives, so the
page populates progressively without a single large request.

Also fixes the artist name in the status bar (was reading wrong field).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/view/maincontent.cpp

@@ -107,3 +107,8 @@ void MainContent::showArtist(const QJsonObject &artist)
     m_artistView->setArtist(artist);
     m_stack->setCurrentIndex(4);
 }
+
+void MainContent::updateArtistReleases(const QString &releaseType, const QJsonArray &items)
+{
+    m_artistView->setReleases(releaseType, items);
+}