fix: resolve Android build issues and create proper plugin module

- Fix capacitor.build.gradle to comment out missing Capacitor integration file
- Create separate plugin module with proper build.gradle configuration
- Copy plugin source code to android/plugin/src/main/java/
- Update settings.gradle to include plugin module
- Fix plugin build.gradle to remove Kotlin plugin dependency
- Successfully build plugin AAR: android/plugin/build/outputs/aar/plugin-release.aar
- Update BUILDING.md with correct build commands and troubleshooting

This resolves the Android Studio build issues by creating a proper
plugin library module separate from the test app.

android/plugin/build.gradle

@@ -0,0 +1,42 @@
+apply plugin: 'com.android.library'
+
+android {
+    namespace "com.timesafari.dailynotification"
+    compileSdkVersion rootProject.ext.compileSdkVersion
+    
+    defaultConfig {
+        minSdkVersion rootProject.ext.minSdkVersion
+        targetSdkVersion rootProject.ext.targetSdkVersion
+        versionCode 1
+        versionName "1.0"
+        
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles "consumer-rules.pro"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+}
+
+dependencies {
+    implementation "androidx.appcompat:appcompat:$androidxAppCompatVersion"
+    implementation "androidx.room:room-runtime:2.6.1"
+    implementation "androidx.work:work-runtime-ktx:2.9.0"
+    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib:1.9.10"
+    
+    annotationProcessor "androidx.room:room-compiler:2.6.1"
+    
+    testImplementation "junit:junit:$junitVersion"
+    androidTestImplementation "androidx.test.ext:junit:$androidxJunitVersion"
+    androidTestImplementation "androidx.test.espresso:espresso-core:$androidxEspressoCoreVersion"
+}