Set up Android project with Kotlin and Jetpack Compose

Initial project structure with manifest configured for foreground
audio service, AudioTrack-based playback, and background operation.
Includes Gradle wrapper, dependency catalog, placeholder icons,
and build instructions for Arch Linux.

.gitignore

@@ -0,0 +1,14 @@
+# Build output
+build/
+app/build/
+
+# Gradle cache
+.gradle/
+
+# Local SDK/IDE config
+local.properties
+*.iml
+.idea/
+
+# Claude Code session data
+.claude/