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/XMenu.qml

@@ -0,0 +1,48 @@
+import QtQuick
+import QtQuick.Controls.Basic
+
+// Office context menu: white, gray border, icon gutter on the left.
+Menu {
+    id: m
+    padding: 2
+    delegate: MenuItem {
+        id: mi
+        implicitWidth: Math.max(200, lab.implicitWidth + 56)
+        implicitHeight: mi.text === "" ? 7 : 26
+        enabled: mi.action ? mi.action.enabled : true
+        contentItem: Item {
+            T {
+                id: lab
+                x: 28
+                anchors.verticalCenter: parent.verticalCenter
+                text: mi.text
+                color: mi.enabled ? X.ink : X.inkFaint
+            }
+            Ico {
+                visible: mi.action && mi.action.icon.name !== ""
+                name: mi.action ? mi.action.icon.name : ""
+                size: 16
+                x: 4
+                anchors.verticalCenter: parent.verticalCenter
+            }
+            Ico {
+                visible: mi.checkable && mi.checked
+                name: "check"
+                size: 14
+                x: 5
+                anchors.verticalCenter: parent.verticalCenter
+            }
+        }
+        background: Rectangle {
+            color: mi.highlighted && mi.enabled ? "#E0E0E0" : "transparent"
+        }
+        arrow: null
+        indicator: null
+    }
+    background: Rectangle {
+        implicitWidth: 200
+        color: "#FFFFFF"
+        border.color: X.menuBorder
+        Rectangle { x: 25; y: 1; width: 1; height: parent.height - 2; color: "#E7E7E7" }
+    }
+}