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

ui/qml/Header.qml

@@ -0,0 +1,25 @@
+// Logo, the screen's name (the version on the menu) and the machine.
+import QtQuick
+
+Rectangle {
+    required property AppState app
+    required property string iconUrl
+    readonly property var titles: ({ review: "Review", password: "Password", applying: app.biosRun ? "BIOS update" : "Applying",
+                                     done: "Done", bios1: "BIOS update", bios2: "BIOS update" })
+    width: parent.width; height: 72; color: Theme.bar
+    Rectangle { anchors.bottom: parent.bottom; width: parent.width; height: 1; color: Theme.line }
+    Row {
+        anchors.left: parent.left; anchors.leftMargin: 40; anchors.verticalCenter: parent.verticalCenter; spacing: 14
+        Image { source: iconUrl; width: 40; height: 40; sourceSize: Qt.size(80, 80); anchors.verticalCenter: parent.verticalCenter }
+        Text { text: "Steamify"; color: Theme.text; font.family: Theme.display; font.pixelSize: 28; font.weight: Font.Bold; anchors.verticalCenter: parent.verticalCenter }
+        Text { readonly property bool menu: app.screen === "menu"
+               text: menu ? "v" + (app.status.version || "") : "/ " + titles[app.screen]
+               color: Theme.faint; font.family: menu ? Theme.mono : Theme.body; font.pixelSize: menu ? 13 : 15; anchors.verticalCenter: parent.verticalCenter }
+    }
+    Rectangle {
+        visible: app.status.steamMachine === true
+        anchors.right: parent.right; anchors.rightMargin: 40; anchors.verticalCenter: parent.verticalCenter
+        height: 34; radius: 17; color: "#1b2330"; width: mt.implicitWidth + 28
+        Text { id: mt; anchors.centerIn: parent; text: "Steam Machine · CachyOS"; color: Theme.label; font.family: Theme.body; font.pixelSize: 14 }
+    }
+}