refactor: migrate from React Native to native Kotlin Android

[rprabhat]

Summary

Complete migration from React Native 0.74.5 to native Kotlin Android with Jetpack Compose. Removes all RN dependencies and replaces with modern Android architecture components.

Changes

Removed (RN-era)

• All React Native source files (src/, ios/, __tests__/, tests/, e2e/)
• RN config files (babel, metro, jest, eslint, tsconfig, detox)
• RN dependencies and lock files
• iOS project files and CocoaPods

Added (Native Kotlin)

• 27 Kotlin source files with MVVM architecture
• 6 Compose screens: ScanScreen, ContactsScreen, EditContactScreen, SettingsScreen (+ inline Review/Save)
• 4 ViewModels with StateFlow
• Room Database for contact persistence
• DataStore Preferences for app settings
• CameraX for camera capture
• ML Kit Text Recognition for OCR
• CardSnap branding (#0066FF primary, Material 3 theme)
• Deep link support (cardscanner://inject?imageUri=...)
• VCard/CSV export via ShareCompat
• Haptic feedback and network monitoring

Tests

• 17 Espresso E2E test suites (Compose Testing)
• 4 JUnit unit tests (ContactParser, VCardGenerator, ContactCard, AppSettings)
• Test infrastructure: GrantPermissionsRule, TestHelpers, ComposeTestRule

Architecture

MVVM Pattern:
- View: Jetpack Compose screens
- ViewModel: StateFlow + Coroutines
- Model: Room entities + DataStore
- Repository: Data access abstraction

Documentation Updates

• Updated AGENTS.md with Kotlin/Compose documentation
• Updated package.json for Android-only project (v2.0.0)

Testing

How to verify

cd android
# Build debug APK
./gradlew assembleDebug

# Run unit tests
./gradlew testDebugUnitTest

# Run E2E tests (requires emulator)
./gradlew connectedAndroidTest

Test Results

• ✅ 20 unit tests passing (ContactParser: 6, AppSettings: 5, VCardGenerator: 4, ContactCard: 5)
• ✅ 17 E2E test suites written and compiling
• ✅ Debug APK builds successfully (34MB)

AI Disclosure

• AI-Generated: Yes
• Model: Qwen 3.6 Plus
• Platform: OpenCode (OhMyOpenCode)
• Human Oversight: fully reviewed

Repository Hygiene

• No debug code (Log.d, TODO, FIXME)
• No secrets
• Lint passes
• All RN artifacts removed
• AGENTS.md updated