feat: artist sections, fav indicator, art scaling fix, volume popup fix

- Artist profile: collapsible Albums / EPs & Singles / Other sections
  keyed on release_type; fetches up to 200 albums per artist
- Favorites: starred icon on favorited tracks, context menu shows
  Add or Remove (not both); IDs cached when fav tracks are loaded
- Shuffle button: one-time shuffle via shuffleNow() without touching
  global shuffle flag, so double-click still plays in order
- Now-playing art: replaced setFixedHeight hack with ArtWidget that
  overrides hasHeightForWidth() — scales smoothly up and down, no min-size
- Volume popup: replaced QMenu (laggy, broken drag) with Qt::Popup QFrame;
  appears below button; fixed size locked at 100% label width

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

src/view/artistview.cpp

@@ -0,0 +1,153 @@
+#include "artistview.hpp"
+#include "albumlistview.hpp"
+
+#include <QVBoxLayout>
+#include <QHBoxLayout>
+#include <QScrollArea>
+#include <QFont>
+#include <QJsonValue>
+
+// ---------------------------------------------------------------------------
+// ArtistSection
+// ---------------------------------------------------------------------------
+
+ArtistSection::ArtistSection(const QString &title, QWidget *parent)
+    : QWidget(parent)
+    , m_baseTitle(title)
+{
+    auto *layout = new QVBoxLayout(this);
+    layout->setContentsMargins(0, 0, 0, 0);
+    layout->setSpacing(0);
+
+    m_toggle = new QToolButton(this);
+    m_toggle->setCheckable(true);
+    m_toggle->setChecked(true);
+    m_toggle->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
+    m_toggle->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed);
+    m_toggle->setStyleSheet(QStringLiteral(
+        "QToolButton { text-align: left; font-weight: bold; padding: 4px 6px;"
+        "  border: none; border-bottom: 1px solid #333; }"
+        "QToolButton:hover { background: #1e1e1e; }"
+    ));
+    updateToggleText(0);
+    layout->addWidget(m_toggle);
+
+    m_list = new AlbumListView(this);
+    layout->addWidget(m_list);
+
+    connect(m_toggle, &QToolButton::toggled, m_list, &AlbumListView::setVisible);
+    connect(m_list, &AlbumListView::albumSelected, this, &ArtistSection::albumSelected);
+}
+
+void ArtistSection::setAlbums(const QJsonArray &albums)
+{
+    m_list->setAlbums(albums);
+    updateToggleText(albums.size());
+}
+
+bool ArtistSection::isEmpty() const
+{
+    return m_list->topLevelItemCount() == 0;
+}
+
+void ArtistSection::updateToggleText(int count)
+{
+    const QString arrow = m_toggle->isChecked() ? QStringLiteral("▼ ") : QStringLiteral("▶ ");
+    const QString text  = count > 0
+        ? QStringLiteral("%1%2  (%3)").arg(arrow, m_baseTitle).arg(count)
+        : arrow + m_baseTitle;
+    m_toggle->setText(text);
+
+    // Keep arrow in sync when toggled
+    disconnect(m_toggle, &QToolButton::toggled, nullptr, nullptr);
+    connect(m_toggle, &QToolButton::toggled, m_list, &AlbumListView::setVisible);
+    connect(m_toggle, &QToolButton::toggled, this, [this, count](bool open) {
+        const QString a = open ? QStringLiteral("▼ ") : QStringLiteral("▶ ");
+        const QString t = count > 0
+            ? QStringLiteral("%1%2  (%3)").arg(a, m_baseTitle).arg(count)
+            : a + m_baseTitle;
+        m_toggle->setText(t);
+    });
+}
+
+// ---------------------------------------------------------------------------
+// ArtistView
+// ---------------------------------------------------------------------------
+
+ArtistView::ArtistView(QWidget *parent)
+    : QWidget(parent)
+{
+    auto *outerLayout = new QVBoxLayout(this);
+    outerLayout->setContentsMargins(8, 8, 8, 8);
+    outerLayout->setSpacing(6);
+
+    m_nameLabel = new QLabel(this);
+    QFont f = m_nameLabel->font();
+    f.setPointSize(f.pointSize() + 4);
+    f.setBold(true);
+    m_nameLabel->setFont(f);
+    outerLayout->addWidget(m_nameLabel);
+
+    m_bioLabel = new QLabel(this);
+    m_bioLabel->setWordWrap(true);
+    m_bioLabel->setAlignment(Qt::AlignTop | Qt::AlignLeft);
+    m_bioLabel->setMaximumHeight(80);
+    outerLayout->addWidget(m_bioLabel);
+
+    // Scrollable sections area
+    auto *scroll = new QScrollArea(this);
+    scroll->setWidgetResizable(true);
+    scroll->setFrameShape(QFrame::NoFrame);
+
+    auto *content = new QWidget(scroll);
+    auto *sectLayout = new QVBoxLayout(content);
+    sectLayout->setContentsMargins(0, 0, 0, 0);
+    sectLayout->setSpacing(8);
+
+    m_secAlbums = new ArtistSection(tr("Albums"), content);
+    m_secEps    = new ArtistSection(tr("EPs & Singles"), content);
+    m_secOther  = new ArtistSection(tr("Other"), content);
+
+    sectLayout->addWidget(m_secAlbums);
+    sectLayout->addWidget(m_secEps);
+    sectLayout->addWidget(m_secOther);
+    sectLayout->addStretch();
+
+    scroll->setWidget(content);
+    outerLayout->addWidget(scroll, 1);
+
+    connect(m_secAlbums, &ArtistSection::albumSelected, this, &ArtistView::albumSelected);
+    connect(m_secEps,    &ArtistSection::albumSelected, this, &ArtistView::albumSelected);
+    connect(m_secOther,  &ArtistSection::albumSelected, this, &ArtistView::albumSelected);
+}
+
+void ArtistView::setArtist(const QJsonObject &artist)
+{
+    m_nameLabel->setText(artist["name"].toString());
+
+    const QString summary = artist["biography"].toObject()["summary"].toString();
+    m_bioLabel->setText(summary);
+    m_bioLabel->setVisible(!summary.isEmpty());
+
+    const QJsonArray allAlbums = artist["albums"].toObject()["items"].toArray();
+
+    QJsonArray albums, eps, other;
+    for (const QJsonValue &v : allAlbums) {
+        const QJsonObject a = v.toObject();
+        const QString rt = a["release_type"].toString();
+        if (rt == QStringLiteral("album"))
+            albums.append(a);
+        else if (rt == QStringLiteral("epSingle"))
+            eps.append(a);
+        else
+            other.append(a);
+    }
+
+    m_secAlbums->setAlbums(albums);
+    m_secEps->setAlbums(eps);
+    m_secOther->setAlbums(other);
+
+    m_secAlbums->setVisible(!m_secAlbums->isEmpty());
+    m_secEps->setVisible(!m_secEps->isEmpty());
+    m_secOther->setVisible(!m_secOther->isEmpty());
+}