Update source code with grid layout and channel management

Major changes:
- Add ChannelAdapter for grid display functionality
- Add ChannelRepository for data management
- Add PlayerActivity for dedicated video playback
- Add StreamChannel model for channel representation
- Update MainActivity to support grid layout
- Update activity_main.xml with grid UI components
- Add channel item layouts and drawables
- Update AndroidManifest.xml with new activity
- Update build.gradle dependencies

This implements the requested "grilla arreglada" functionality with proper channel grid display and management.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/src/main/res/drawable/bg_channel_item.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <solid android:color="#33212121" />
+    <corners android:radius="12dp" />
+    <stroke
+        android:width="1dp"
+        android:color="#55FFFFFF" />
+</shape>

app/src/main/res/drawable/ic_channel_default.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M21,6h-7.59l2.3,-2.29c0.63,-0.63 0.19,-1.71 -0.7,-1.71H8.99c-0.89,0 -1.33,1.08 -0.7,1.71L10.59,6H3c-1.11,0 -2,0.9 -2,2v12c0,1.1 0.89,2 2,2h18c1.11,0 2,-0.9 2,-2L23,8c0,-1.1 -0.89,-2 -2,-2zM21,18H3L3,8h18v10z" />
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M9,10h2v6L9,16zM13,10h2v6h-2z" />
+</vector>