start kotlin/jetpack compose rewrite

replace the flutter project with a gradle/compose android app:
- nix flake dev shell (jdk21, android sdk 35, build-tools 37, gradle)
- material3 app with a placeholder screen
- roborazzi/robolectric screenshot tests with one golden
- carry over the existing launcher/notification assets

.gitignore

@@ -1,49 +1,17 @@
-# Miscellaneous
-*.class
-*.log
-*.pyc
-*.swp
-.DS_Store
-.atom/
-.buildlog/
-.history
-.svn/
-migrate_working_dir/
+.gradle/
+build/
+local.properties
+
+*.apk
+*.aab
+captures/
+.cxx/
 
-# IntelliJ related
-*.iml
-*.ipr
-*.iws
 .idea/
+*.iml
+.vscode/
 
-# The .vscode folder contains launch configuration and tasks you configure in
-# VS Code which you may wish to be included in version control, so this line
-# is commented out by default.
-#.vscode/
+.kotlin/
+.preview/
 
-# Flutter/Dart/Pub related
-**/doc/api/
-**/ios/Flutter/.last_build_id
-.dart_tool/
-.flutter-plugins
-.flutter-plugins-dependencies
-.packages
-.pub-cache/
-.pub/
-/build/
-
-# Symbolication related
-app.*.symbols
-
-# Obfuscation related
-app.*.map.json
-
-# Android Studio will place build artifacts here
-/android/app/debug
-/android/app/profile
-/android/app/release
-
-/.env
-*.sqlite*
-/.fvm/flutter_sdk
-*.keystore
+.DS_Store