feat(android): implement private Rust storage runtime (#90)

android/platform/src/main/kotlin/de/rfc1437/ironstorage/platform/PrivateDirectoryProvider.kt

@@ -0,0 +1,11 @@
+package de.rfc1437.ironstorage.platform
+
+import android.content.Context
+import de.rfc1437.ironstorage.core.PrivateDirectories
+
+/** Only Context's OS directory facts; Rust owns all subordinate paths and files. */
+fun privateDirectories(context: Context): PrivateDirectories = PrivateDirectories(
+    context.filesDir.canonicalPath,
+    context.noBackupFilesDir.canonicalPath,
+    context.cacheDir.canonicalPath
+)