chore: ignore Android build leftovers and signing files

.gitignore

@@ -17,3 +17,32 @@ output/
 !.env.example
 *.sqlite*
 *.log
+
+# Local IDE files
+.idea/
+*.iml
+
+# Generated files left when switching from android-app
+/.dart_tool/
+/.flutter-plugins-dependencies
+/build/
+/android/.gradle/
+/android/.kotlin/
+/android/build/
+/android/app/build/
+/android/local.properties
+/android/gradlew
+/android/gradlew.bat
+/android/gradle/wrapper/gradle-wrapper.jar
+/android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java
+
+# Android packages and signing credentials
+*.apk
+*.aab
+*.jks
+*.keystore
+*.p12
+*.pfx
+keystore.properties
+signing.properties
+/android/key.properties