Segunda revisión completa: fixes críticos aplicados

- StrictMode solo en DEBUG mode
- ExecutorService con shutdown apropiado
- DNSSetter NetworkCallback unregister
- DiffUtil en ChannelAdapter y EventAdapter
- minifyEnabled=true y shrinkResources=true para release
- Validación en constructores (StreamChannel)
- Strings externalizadas
- ProGuard rules completas
- Testing dependencies agregadas
- Removed Firebase (uso personal)
- JavaDoc documentación agregada
- Android SDK configurado localmente

Compilado exitosamente: StreamPlayer v9.4.2 debug APK (11MB)

src/androidTest/java/com/renato/streamplayer/ExampleInstrumentedTest.java

@@ -0,0 +1,26 @@
+package com.renato.streamplayer;
+
+import android.content.Context;
+
+import androidx.test.platform.app.InstrumentationRegistry;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static org.junit.Assert.*;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+    @Test
+    public void useAppContext() {
+        // Context of the app under test.
+        Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
+        assertEquals("com.renato.streamplayer", appContext.getPackageName());
+    }
+}

src/test/java/com/renato/streamplayer/ExampleUnitTest.java

@@ -0,0 +1,17 @@
+package com.renato.streamplayer;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+public class ExampleUnitTest {
+    @Test
+    public void addition_isCorrect() {
+        assertEquals(4, 2 + 2);
+    }
+}