fix(calamares-branding-antergos-next-minimal): comprehensive dark QSS — cover all Calamares widgets

Previous QSS only styled QMainWindow, QPushButton, QComboBox, QLineEdit,
and QProgressBar. Unstyled widgets (QListView, QTreeView, QGroupBox,
QRadioButton, QCheckBox, QScrollBar, QTabWidget, QHeaderView, etc.)
rendered with white backgrounds from the default Qt theme, making text
invisible in the Xfce live environment (no Plasma/Breeze dark).

New QSS covers every widget Calamares uses, with dark backgrounds
(#20252B / #262C34 / #2C3138) and Antergos blue (#4A9EFF) accents.

packages/calamares-branding-antergos-next-minimal/stylesheet.qss

@@ -2,10 +2,18 @@
 QWidget {
     font-family: "Noto Sans", "DejaVu Sans", sans-serif;
     font-size: 10pt;
-    color: #FFFFFF;
 }
-QMainWindow {
+QMainWindow, QDialog, QWizard, QWidget#sidebar {
     background-color: #20252B;
+    color: #C8D6E5;
+}
+QWidget#mainContent, QScrollArea, QFrame, QStackedWidget {
+    background-color: #20252B;
+    color: #C8D6E5;
+}
+QLabel {
+    color: #C8D6E5;
+    background: transparent;
 }
 QLabel#titleLabel {
     font-size: 18pt;
@@ -16,6 +24,21 @@ QLabel#subtitleLabel {
     font-size: 11pt;
     color: #C8D6E5;
 }
+QGroupBox {
+    background-color: #262C34;
+    border: 1px solid #3A3F47;
+    border-radius: 4px;
+    margin-top: 12px;
+    padding: 12px 8px 8px 8px;
+    color: #C8D6E5;
+    font-weight: bold;
+}
+QGroupBox::title {
+    subcontrol-origin: margin;
+    subcontrol-position: top left;
+    padding: 2px 8px;
+    color: #4A9EFF;
+}
 QPushButton {
     background-color: #4A9EFF;
     color: white;
@@ -41,13 +64,155 @@ QComboBox {
     border-radius: 4px;
     background: #2C3138;
     color: #FFFFFF;
+    min-height: 24px;
 }
-QLineEdit {
+QComboBox::drop-down {
+    border: none;
+    width: 24px;
+}
+QComboBox::down-arrow {
+    image: none;
+    border-left: 5px solid transparent;
+    border-right: 5px solid transparent;
+    border-top: 6px solid #C8D6E5;
+    margin-right: 6px;
+}
+QComboBox QAbstractItemView {
+    background: #2C3138;
+    color: #C8D6E5;
+    selection-background-color: #4A9EFF;
+    selection-color: #FFFFFF;
+    border: 1px solid #3A3F47;
+    outline: none;
+}
+QLineEdit, QSpinBox, QDoubleSpinBox {
     padding: 6px 10px;
     border: 1px solid #3A3F47;
     border-radius: 4px;
     background: #2C3138;
     color: #FFFFFF;
+    min-height: 20px;
+}
+QTextEdit, QPlainTextEdit {
+    border: 1px solid #3A3F47;
+    border-radius: 4px;
+    background: #2C3138;
+    color: #C8D6E5;
+    padding: 4px;
+}
+QListView, QTreeView, QTableView {
+    background: #2C3138;
+    color: #C8D6E5;
+    border: 1px solid #3A3F47;
+    border-radius: 4px;
+    outline: none;
+    alternate-background-color: #262C34;
+}
+QListView::item, QTreeView::item, QTableView::item {
+    padding: 4px 8px;
+    min-height: 24px;
+    border: none;
+}
+QListView::item:selected, QTreeView::item:selected, QTableView::item:selected {
+    background: #4A9EFF;
+    color: #FFFFFF;
+}
+QListView::item:hover, QTreeView::item:hover, QTableView::item:hover {
+    background: #3A3F47;
+}
+QHeaderView::section {
+    background: #1A1F24;
+    color: #C8D6E5;
+    padding: 4px 8px;
+    border: none;
+    border-right: 1px solid #3A3F47;
+    border-bottom: 1px solid #3A3F47;
+    font-weight: bold;
+}
+QScrollBar:vertical {
+    background: #1A1F24;
+    width: 10px;
+    margin: 0;
+}
+QScrollBar::handle:vertical {
+    background: #3A3F47;
+    border-radius: 5px;
+    min-height: 30px;
+}
+QScrollBar::handle:vertical:hover {
+    background: #4A9EFF;
+}
+QScrollBar::add-line:vertical, QScrollBar::sub-line:vertical {
+    height: 0;
+    background: transparent;
+}
+QScrollBar::add-page:vertical, QScrollBar::sub-page:vertical {
+    background: transparent;
+}
+QScrollBar:horizontal {
+    background: #1A1F24;
+    height: 10px;
+    margin: 0;
+}
+QScrollBar::handle:horizontal {
+    background: #3A3F47;
+    border-radius: 5px;
+    min-width: 30px;
+}
+QScrollBar::handle:horizontal:hover {
+    background: #4A9EFF;
+}
+QScrollBar::add-line:horizontal, QScrollBar::sub-line:horizontal {
+    width: 0;
+    background: transparent;
+}
+QScrollBar::add-page:horizontal, QScrollBar::sub-page:horizontal {
+    background: transparent;
+}
+QRadioButton, QCheckBox {
+    color: #C8D6E5;
+    spacing: 6px;
+    min-height: 22px;
+}
+QRadioButton::indicator, QCheckBox::indicator {
+    width: 16px;
+    height: 16px;
+    border: 2px solid #3A3F47;
+    border-radius: 8px;
+    background: #2C3138;
+}
+QRadioButton::indicator:checked, QCheckBox::indicator:checked {
+    background: #4A9EFF;
+    border-color: #4A9EFF;
+}
+QRadioButton::indicator:hover, QCheckBox::indicator:hover {
+    border-color: #4A9EFF;
+}
+QCheckBox::indicator {
+    border-radius: 3px;
+}
+QCheckBox::indicator:checked {
+    image: none;
+}
+QTabWidget::pane {
+    background: #262C34;
+    border: 1px solid #3A3F47;
+    border-radius: 4px;
+}
+QTabBar::tab {
+    background: #1A1F24;
+    color: #7F8C8D;
+    padding: 6px 16px;
+    border: none;
+    min-height: 24px;
+}
+QTabBar::tab:selected {
+    background: #262C34;
+    color: #FFFFFF;
+    border-bottom: 2px solid #4A9EFF;
+}
+QTabBar::tab:hover {
+    color: #C8D6E5;
 }
 QProgressBar {
     border: 1px solid #3A3F47;
@@ -62,3 +227,20 @@ QProgressBar::chunk {
         stop:0 #4A9EFF, stop:1 #8BC4FF);
     border-radius: 3px;
 }
+QSpinBox::up-button, QDoubleSpinBox::up-button {
+    border: none;
+    background: transparent;
+    width: 20px;
+}
+QSpinBox::down-button, QDoubleSpinBox::down-button {
+    border: none;
+    background: transparent;
+    width: 20px;
+}
+QToolTip {
+    background: #20252B;
+    color: #C8D6E5;
+    border: 1px solid #4A9EFF;
+    padding: 4px 8px;
+    border-radius: 4px;
+}