feat(android): add API client, tRPC bridge, and offline support

- Add Retrofit with kotlinx-serialization converter for tRPC endpoints
- Create TRPCApiService with type-safe wrappers for all procedures
- Implement AuthInterceptor for JWT injection from EncryptedSharedPreferences
- Add ErrorHandler with exponential backoff retry logic and ApiResult sealed class
- Create 11 serializable data models matching backend enums
- Add JSON file-based cache with TTL invalidation (CacheManager)
- Implement repositories: User, DarkWatch, VoicePrint, Alert, Subscription
- Add offline sync: PendingRequestQueue, OfflineWorker, SyncManager
- Create manual DI modules: NetworkModule, DatabaseModule, RepositoryModule
- Add WorkManager for background offline request processing
- Add ConnectivityManager-based network monitoring for auto-sync
- Configure build system with KSP for Room, kotlinx-serialization plugin
- Update build config with environment-specific API URLs
- Write 19 new unit tests for ErrorHandler, CacheManager, TRPCResponse, SyncManager

android/ShieldAI/build.gradle.kts

@@ -1,5 +1,5 @@
-// Top-level build file where you can add configuration options common to all sub-projects/modules.
 plugins {
     alias(libs.plugins.android.application) apply false
     alias(libs.plugins.kotlin.compose) apply false
-}
+    alias(libs.plugins.kotlin.serialization) apply false
+}