Migrate to Kotlin and Jetpack Compose with modern architecture

Major refactoring to modernize the codebase:

- Migrated all Java activities to Kotlin
  - MainActivity.kt with Compose UI
  - FilePickerActivity.kt with Compose UI
  - ProgressActivity.kt with Compose UI

- Implemented MVVM architecture with ViewModel pattern
  - MainViewModel with StateFlow for reactive state management
  - FilePickerViewModel for file navigation state
  - ProgressViewModel with coroutine-based polling

- Migrated all UI to Jetpack Compose
  - Material 3 design system
  - Dark theme with Purple80 accent colors
  - Custom composables in ui/ package
  - Removed legacy XML layouts

- Fixed batch progress bug: When multiple RPA files are selected,
  the progress screen now correctly displays batch information
  (e.g., "Extracting RPA... (2 of 5)") using ViewModel state

- Improved code organization
  - ViewModels in viewmodel/ package
  - Composables in ui/ package
  - Better separation of concerns

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

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

Author: Sirpixelalittle

app/build.gradle

@@ -1,5 +1,7 @@
 plugins {
     alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.android)
+    alias(libs.plugins.kotlin.compose)
     id 'com.chaquo.python'
 }
 
@@ -58,14 +60,46 @@ android {
         sourceCompatibility JavaVersion.VERSION_17
         targetCompatibility JavaVersion.VERSION_17
     }
+
+    kotlinOptions {
+        jvmTarget = '17'
+    }
+
+    buildFeatures {
+        compose = true
+    }
 }
 
 dependencies {
+    // AndroidX Core
     implementation libs.appcompat
     implementation libs.material
     implementation 'androidx.coordinatorlayout:coordinatorlayout:1.2.0'
     implementation 'androidx.documentfile:documentfile:1.0.1'
 
+    // Compose BOM (manages Compose versions)
+    implementation platform(libs.compose.bom)
+    implementation libs.compose.ui
+    implementation libs.compose.ui.tooling.preview
+    implementation libs.compose.material3
+    implementation libs.compose.material.icons.extended
+    debugImplementation libs.compose.ui.tooling
+    debugImplementation libs.compose.ui.test.manifest
+
+    // Compose Integration
+    implementation libs.activity.compose
+    implementation libs.lifecycle.viewmodel.compose
+    implementation libs.lifecycle.runtime.compose
+    implementation libs.navigation.compose
+
+    // Lifecycle & ViewModel
+    implementation libs.lifecycle.viewmodel.ktx
+    implementation libs.lifecycle.runtime.ktx
+
+    // Coroutines
+    implementation libs.kotlinx.coroutines.android
+    implementation libs.kotlinx.coroutines.core
+
     // JSON parsing for update checker
     implementation 'com.google.code.gson:gson:2.10.1'
 
@@ -74,6 +108,7 @@ dependencies {
     implementation 'io.github.rosemoe:editor'
     implementation 'io.github.rosemoe:language-textmate'
 
+    // Testing
     testImplementation libs.junit
     androidTestImplementation libs.ext.junit
     androidTestImplementation libs.espresso.core