StemRoller: desktop stem separator, Android stems player, and server daemons

- stemroller/: PySide6/QML desktop app and player for separating music into stems
- android/: Plex music player that plays per-stem mixes, with Android Auto support,
  a graphic + parametric (Equalizer APO-style) EQ, and offline downloads
- server/: stemserve (serves stems to the app) and stemd (separates the library on
  the server's GPU, with "Stem Now" priority requests)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

stemroller/player/qml/StemPlayer/OfficeButton.qml

@@ -0,0 +1,16 @@
+import QtQuick
+
+// Dialog button: gray with a border; the default one outlined in green.
+Rectangle {
+    id: ob
+    property string text
+    property bool primary: false
+    signal clicked()
+    implicitWidth: Math.max(80, t.implicitWidth + 24)
+    implicitHeight: 26
+    color: m.pressed ? "#CCE4F7" : m.containsMouse ? "#E5F1FB" : "#FDFDFD"
+    border.color: m.containsMouse ? "#0078D7" : primary ? X.green : "#ADADAD"
+    border.width: primary ? 2 : 1
+    T { id: t; anchors.centerIn: parent; text: ob.text }
+    MouseArea { id: m; anchors.fill: parent; hoverEnabled: true; onClicked: ob.clicked() }
+}