feat: ambient scene system + unlock-screen banner (reduced-motion aware)

Reusable SceneWidget (QQuickWidget host) loads scene.qml — dusk sky, tiled
grass, running doge, bouncing WOW coins (slowed per feedback), drifting
money — and feeds it Config::reducedMotion so it freezes to a still when
that's set. First placement: a banner atop the unlock form. Scene rendered
& verified at banner + screensaver aspects via local qml6 harness. Assets
from wow-lite-wallet (friend's). Home banner / idle screensaver / per-tab
idle to follow on the same SceneWidget.

src/widgets/SceneWidget.cpp

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// SPDX-FileCopyrightText: The Monero Project
+
+#include "SceneWidget.h"
+
+#include <QQmlContext>
+
+#include "utils/config.h"
+
+SceneWidget::SceneWidget(QWidget *parent)
+    : QQuickWidget(parent)
+    , m_backend(new SceneBackend(this))
+{
+    m_backend->setReducedMotion(conf()->get(Config::reducedMotion).toBool());
+    this->rootContext()->setContextProperty("sceneCtx", m_backend);
+    this->setResizeMode(QQuickWidget::SizeRootObjectToView);
+    this->setSource(QUrl("qrc:/qml/scene.qml"));
+}
+
+void SceneWidget::refreshReducedMotion() {
+    m_backend->setReducedMotion(conf()->get(Config::reducedMotion).toBool());
+}

src/widgets/SceneWidget.h

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: BSD-3-Clause
+// SPDX-FileCopyrightText: The Monero Project
+
+#ifndef WOWLET_SCENEWIDGET_H
+#define WOWLET_SCENEWIDGET_H
+
+#include <QObject>
+#include <QQuickWidget>
+
+// Context object exposed to scene.qml as `sceneCtx`. Carries the reduced-motion
+// setting so the scene freezes into its still (reduced-motion) form.
+class SceneBackend : public QObject {
+Q_OBJECT
+    Q_PROPERTY(bool reducedMotion READ reducedMotion NOTIFY reducedMotionChanged)
+public:
+    explicit SceneBackend(QObject *parent = nullptr) : QObject(parent) {}
+    bool reducedMotion() const { return m_reducedMotion; }
+    void setReducedMotion(bool r) { if (m_reducedMotion != r) { m_reducedMotion = r; emit reducedMotionChanged(); } }
+signals:
+    void reducedMotionChanged();
+private:
+    bool m_reducedMotion = false;
+};
+
+// wowlet: reusable ambient-scene surface. Hosts scene.qml and reads the
+// reduced-motion preference from Config. Drop it behind a form, into a banner,
+// or over the window as an idle screensaver.
+class SceneWidget : public QQuickWidget {
+Q_OBJECT
+public:
+    explicit SceneWidget(QWidget *parent = nullptr);
+    void refreshReducedMotion();
+private:
+    SceneBackend *m_backend;
+};
+
+#endif //WOWLET_SCENEWIDGET_H

src/widgets/WalletUnlockWidget.cpp

@@ -9,6 +9,7 @@
 
 #include "utils/Utils.h"
 #include "libwalletqt/Wallet.h"
+#include "widgets/SceneWidget.h"
 
 WalletUnlockWidget::WalletUnlockWidget(QWidget *parent, Wallet *wallet)
         : QWidget(parent)
@@ -18,6 +19,13 @@ WalletUnlockWidget::WalletUnlockWidget(QWidget *parent, Wallet *wallet)
     ui->setupUi(this);
     this->reset();
 
+    // wowlet: ambient scene banner above the unlock form (freezes itself into a
+    // still when "Prefer reduced motion" is set).
+    auto *scene = new SceneWidget(this);
+    scene->setMinimumHeight(120);
+    scene->setMaximumHeight(140);
+    ui->verticalLayout->insertWidget(0, scene);
+
     ui->buttonBox->button(QDialogButtonBox::Ok)->setAutoDefault(true);
 
     connect(ui->buttonBox, &QDialogButtonBox::accepted, this, &WalletUnlockWidget::tryUnlock);