improved android client, feature parity with desktop

android/app/proguard-rules.pro

@@ -7,3 +7,19 @@
 -keepclasseswithmembernames class * {
     native <methods>;
 }
+
+# UniFFI records are Kotlin data classes whose generic signatures and
+# annotations survive into the runtime; stripping them changes how the bindings
+# lift and lower structured types.
+-keepattributes Signature,*Annotation*,InnerClasses,EnclosingMethod
+
+# JNA dispatches into callbacks reflectively by method name.
+-keepclassmembers class * implements com.sun.jna.Callback {
+    <methods>;
+}
+
+# The bridge calls back into these from Rust. Nothing in the Kotlin call graph
+# reaches their overrides, so R8 is free to rename or drop them.
+-keep class io.narl.protonstream.native.KeystoreSecretStore { *; }
+-keep class * implements uniffi.pstr_android.AndroidSecretStore { *; }
+-keep class * implements uniffi.pstr_android.DownloadObserver { *; }