refactor: make LNbitsHttpClient.instance internal

app/src/main/java/com/bitcointxoko/gudariwallet/api/LNbitsHttpClient.kt

@@ -4,12 +4,13 @@ import com.bitcointxoko.gudariwallet.util.WalletConstants
 import okhttp3.OkHttpClient
 import java.util.concurrent.TimeUnit
 
-/**
- * Single shared OkHttpClient for the entire app.
- * Used by both LNbitsClient (Retrofit) and WalletNotificationService (WebSocket).
- */
+// internal = visible within this Gradle module only.
+// Intentionally not private: WalletNotificationService accesses this
+// directly because Android instantiates Services via reflection —
+// constructor injection is not possible. All other consumers must use
+// LNbitsClient.api instead.
 object LNbitsHttpClient {
-    val instance: OkHttpClient = OkHttpClient.Builder()
+    internal val instance: OkHttpClient = OkHttpClient.Builder()
         .connectTimeout(WalletConstants.CONNECT_TIMEOUT_S, TimeUnit.SECONDS)
         .readTimeout(WalletConstants.READ_TIMEOUT_S, TimeUnit.SECONDS)
         .writeTimeout(WalletConstants.WRITE_TIMEOUT_S, TimeUnit.SECONDS)