Feat: Android client device grouping with persistent group name

- szPCName sent as "model/groupName" format matching Linux client
- CMD_SET_GROUP handler updates g_SETTINGS.szGroupName in memory
- Group name persisted to filesDir/yama_group; survives process restart
- LoadGroupName() at startup overrides build-time patch value if file exists

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

android/app/src/main/java/com/yama/client/YamaBridge.kt

@@ -13,7 +13,8 @@ object YamaBridge {
         androidVersion: String,
         screenRes: String,
         username: String,
-        apkPath: String
+        apkPath: String,
+        filesDir: String
     ): Int
 
     external fun nativeStop()