fix: include native module sources in git tracking

Fix .gitignore to only exclude root android/ and ios/
(Expo prebuild output) while keeping modules/ native code.
Add Android WallpaperService Kotlin sources, GLSL shaders,
manifest, and Gradle config.

modules/wallpaper-android/android/build.gradle.kts

@@ -0,0 +1,27 @@
+plugins {
+  id("com.android.library")
+  id("org.jetbrains.kotlin.android")
+}
+
+android {
+  namespace = "com.lively.wallpaper"
+  compileSdk = 35
+
+  defaultConfig {
+    minSdk = 24
+  }
+
+  compileOptions {
+    sourceCompatibility = JavaVersion.VERSION_17
+    targetCompatibility = JavaVersion.VERSION_17
+  }
+
+  kotlinOptions {
+    jvmTarget = "17"
+  }
+}
+
+dependencies {
+  implementation(project(":expo-modules-core"))
+  implementation("org.jetbrains.kotlin:kotlin-stdlib")
+}