chore: configure for Play Store release

- Change application ID to id.ptsemangat.siab_scale
- Move Kotlin package to id/ptsemangat/siab_scale
- Update iOS/macOS/Linux/Windows bundle identifiers
- Configure release signing in both build.gradle files
- Add proguard-rules.pro
- Add key.properties.example template
- Add privacy policy placeholders (en/id)
- Add Gitea CI workflow for AAB builds
- Add RELEASE_CHECKLIST.md
- Update copyrights to PT. Semangat Inovasi Anak Bangsa

android/key.properties.example

@@ -0,0 +1,11 @@
+# Release signing configuration for SIAB Scale
+# DO NOT commit this file to version control!
+#
+# Generate keystore:
+#   keytool -genkey -v -keystore siab-release.keystore -alias siab -keyalg RSA -keysize 2048 -validity 10000
+#
+# Fill in your passwords below:
+storePassword=CHANGE_ME_STORE_PASSWORD
+keyPassword=CHANGE_ME_KEY_PASSWORD
+keyAlias=siab
+storeFile=../siab-release.keystore