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>

.gitignore

@@ -0,0 +1,18 @@
+# Python
+.venv/
+__pycache__/
+*.pyc
+
+# Android / Gradle
+android/.gradle/
+android/.kotlin/
+android/build/
+android/app/build/
+android/local.properties
+android/captures/
+.idea/
+*.iml
+
+# Built and third-party APKs (publish builds as GitHub Releases instead)
+*.apk
+*.aab