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/qml/StemRoller/AeroSlider.qml

@@ -0,0 +1,46 @@
+import QtQuick
+import QtQuick.Controls.Basic
+
+Slider {
+    id: s
+    property color tone: Theme.primary
+    implicitHeight: 24
+    hoverEnabled: true
+    background: Rectangle {
+        x: s.leftPadding
+        y: s.topPadding + s.availableHeight / 2 - height / 2
+        width: s.availableWidth
+        height: 4
+        radius: 2
+        color: Qt.rgba(1, 1, 1, 0.10)
+        Rectangle {
+            width: s.visualPosition * parent.width
+            height: parent.height
+            radius: 2
+            gradient: Gradient {
+                orientation: Gradient.Horizontal
+                GradientStop { position: 0; color: Theme.alpha(s.tone, 0.7) }
+                GradientStop { position: 1; color: s.tone }
+            }
+        }
+    }
+    handle: Item {
+        x: s.leftPadding + s.visualPosition * (s.availableWidth - width)
+        y: s.topPadding + s.availableHeight / 2 - height / 2
+        width: 14
+        height: 14
+        Glow { radius: 7; sigma: 4; color: s.tone; opacity: s.hovered || s.pressed ? 0.6 : 0 }
+        Rectangle {
+            anchors.fill: parent
+            radius: 7
+            color: s.pressed ? Qt.lighter(s.tone, 1.2) : s.tone
+            border.color: Qt.lighter(s.tone, 1.4)
+            Rectangle {  // gloss
+                anchors { left: parent.left; right: parent.right; top: parent.top; margins: 2 }
+                height: 5
+                radius: 3
+                color: Qt.rgba(1, 1, 1, 0.45)
+            }
+        }
+    }
+}