Initial implementation of qobuz-qt

- Rust backend (qobuz-backend static lib): Qobuz API client (reqwest/tokio),
  Symphonia audio decoder, CPAL audio output, extern "C" FFI bridge
- Qt 6 frontend mirroring spotify-qt layout: toolbar with playback controls,
  left library dock, central track list, right search panel
- Auth: email/password login with MD5-signed requests; session token persisted
  via QSettings
- Playback: double-click a track → Rust fetches stream URL → Symphonia decodes
  → CPAL outputs to default audio device
- Dark Fusion palette matching spotify-qt feel

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

src/dialog/login.cpp

@@ -0,0 +1,80 @@
+#include "login.hpp"
+
+#include <QVBoxLayout>
+#include <QFormLayout>
+#include <QHBoxLayout>
+#include <QDialogButtonBox>
+
+LoginDialog::LoginDialog(QWidget *parent) : QDialog(parent)
+{
+    setWindowTitle(tr("Sign in to Qobuz"));
+    setMinimumWidth(360);
+    setModal(true);
+
+    auto *layout = new QVBoxLayout(this);
+    layout->setSpacing(12);
+
+    // Logo / title
+    auto *title = new QLabel(QStringLiteral("<h2>Qobuz</h2>"), this);
+    title->setAlignment(Qt::AlignCenter);
+    layout->addWidget(title);
+
+    // Form
+    auto *form = new QFormLayout;
+    form->setLabelAlignment(Qt::AlignRight);
+
+    m_email    = new QLineEdit(this);
+    m_password = new QLineEdit(this);
+    m_password->setEchoMode(QLineEdit::Password);
+
+    form->addRow(tr("E-mail:"),   m_email);
+    form->addRow(tr("Password:"), m_password);
+    layout->addLayout(form);
+
+    // Remember checkbox
+    m_remember = new QCheckBox(tr("Remember me"), this);
+    m_remember->setChecked(true);
+    layout->addWidget(m_remember);
+
+    // Error label (hidden until needed)
+    m_errorLbl = new QLabel(this);
+    m_errorLbl->setStyleSheet("color: red;");
+    m_errorLbl->setWordWrap(true);
+    m_errorLbl->hide();
+    layout->addWidget(m_errorLbl);
+
+    // Buttons
+    m_loginBtn = new QPushButton(tr("Sign in"), this);
+    m_loginBtn->setDefault(true);
+    auto *cancelBtn = new QPushButton(tr("Cancel"), this);
+
+    auto *btnLayout = new QHBoxLayout;
+    btnLayout->addStretch();
+    btnLayout->addWidget(cancelBtn);
+    btnLayout->addWidget(m_loginBtn);
+    layout->addLayout(btnLayout);
+
+    connect(m_loginBtn, &QPushButton::clicked, this, [this] {
+        m_errorLbl->hide();
+        emit loginRequested(m_email->text().trimmed(), m_password->text());
+    });
+    connect(cancelBtn, &QPushButton::clicked, this, &QDialog::reject);
+
+    // Allow pressing Enter in the password field
+    connect(m_password, &QLineEdit::returnPressed, m_loginBtn, &QPushButton::click);
+}
+
+void LoginDialog::setError(const QString &msg)
+{
+    m_errorLbl->setText(msg);
+    m_errorLbl->show();
+    setBusy(false);
+}
+
+void LoginDialog::setBusy(bool busy)
+{
+    m_loginBtn->setEnabled(!busy);
+    m_loginBtn->setText(busy ? tr("Signing in…") : tr("Sign in"));
+    m_email->setEnabled(!busy);
+    m_password->setEnabled(!busy);
+}

src/dialog/login.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <QDialog>
+#include <QLineEdit>
+#include <QPushButton>
+#include <QLabel>
+#include <QCheckBox>
+
+class LoginDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit LoginDialog(QWidget *parent = nullptr);
+
+    QString email()    const { return m_email->text(); }
+    QString password() const { return m_password->text(); }
+    bool    remember() const { return m_remember->isChecked(); }
+
+    void setError(const QString &msg);
+    void setBusy(bool busy);
+
+signals:
+    void loginRequested(const QString &email, const QString &password);
+
+private:
+    QLineEdit   *m_email    = nullptr;
+    QLineEdit   *m_password = nullptr;
+    QCheckBox   *m_remember = nullptr;
+    QPushButton *m_loginBtn = nullptr;
+    QLabel      *m_errorLbl = nullptr;
+};

src/dialog/settings.cpp

@@ -0,0 +1,54 @@
+#include "settings.hpp"
+#include "../util/settings.hpp"
+
+#include <QVBoxLayout>
+#include <QFormLayout>
+#include <QDialogButtonBox>
+#include <QGroupBox>
+
+SettingsDialog::SettingsDialog(QWidget *parent) : QDialog(parent)
+{
+    setWindowTitle(tr("Settings"));
+    setMinimumWidth(400);
+
+    auto *layout = new QVBoxLayout(this);
+
+    // --- Playback group ---
+    auto *playGroup  = new QGroupBox(tr("Playback"), this);
+    auto *playLayout = new QFormLayout(playGroup);
+
+    m_formatBox = new QComboBox(playGroup);
+    m_formatBox->addItem(tr("Hi-Res 24-bit/192kHz"), 27);
+    m_formatBox->addItem(tr("Hi-Res 24-bit/96kHz"),  7);
+    m_formatBox->addItem(tr("CD 16-bit"),             6);
+    m_formatBox->addItem(tr("MP3 320 kbps"),          5);
+
+    const int currentFormat = AppSettings::instance().preferredFormat();
+    for (int i = 0; i < m_formatBox->count(); ++i) {
+        if (m_formatBox->itemData(i).toInt() == currentFormat) {
+            m_formatBox->setCurrentIndex(i);
+            break;
+        }
+    }
+
+    playLayout->addRow(tr("Preferred quality:"), m_formatBox);
+    layout->addWidget(playGroup);
+
+    layout->addStretch();
+
+    auto *buttons = new QDialogButtonBox(
+        QDialogButtonBox::Ok | QDialogButtonBox::Cancel, this);
+    layout->addWidget(buttons);
+
+    connect(buttons, &QDialogButtonBox::accepted, this, [this] {
+        applyChanges();
+        accept();
+    });
+    connect(buttons, &QDialogButtonBox::rejected, this, &QDialog::reject);
+}
+
+void SettingsDialog::applyChanges()
+{
+    AppSettings::instance().setPreferredFormat(
+        m_formatBox->currentData().toInt());
+}

src/dialog/settings.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <QDialog>
+#include <QComboBox>
+#include <QLabel>
+
+class SettingsDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit SettingsDialog(QWidget *parent = nullptr);
+
+private:
+    QComboBox *m_formatBox = nullptr;
+
+    void applyChanges();
+};