chore: añadir proyecto nativo Android al repositorio

Elimina /android del .gitignore y committea el resultado de
expo prebuild --platform android (Gradle, AndroidManifest, MainActivity,
recursos de icono/splash). Android Studio puede abrirlo directamente
desde la carpeta android/ sin necesidad de ejecutar prebuild.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/proguard-rules.pro

@@ -0,0 +1,14 @@
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in /usr/local/Cellar/android-sdk/24.3.3/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the proguardFiles
+# directive in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# react-native-reanimated
+-keep class com.swmansion.reanimated.** { *; }
+-keep class com.facebook.react.turbomodule.** { *; }
+
+# Add any project specific keep options here: