refactor(ui): One QML file per screen; the HDMI boost's setup screens and backend commands removed

ui/qml/Glyph.qml

@@ -0,0 +1,13 @@
+// A button name (A, Enter, OK...), round for a controller's face buttons.
+import QtQuick
+
+Rectangle {
+    id: glyph
+    property string k
+    property bool dark: false
+    height: 26; width: Math.max(26, gt.implicitWidth + 14)
+    radius: Input.type === "controller" && k.length === 1 ? 13 : 7
+    color: dark ? Theme.ink : Theme.key
+    Text { id: gt; anchors.centerIn: parent; text: glyph.k; color: glyph.dark ? Theme.accent : Theme.textHi
+           font.family: Theme.body; font.pixelSize: 12; font.weight: Font.DemiBold }
+}