Implement Android subscription system with freemium limitations

Major subscription system implementation for Android:

BillingManager (Android):
- Full Google Play Billing Library integration
- Product loading, purchase flow, and acknowledgment
- Backend verification via APILayer.verifyAndroidPurchase()
- Purchase restoration for returning users
- Error handling and connection state management

SubscriptionHelper (Shared):
- New limit checking methods: isResidencesBlocked(), isTasksBlocked(),
  isContractorsBlocked(), isDocumentsBlocked()
- Add permission checks: canAddProperty(), canAddTask(),
  canAddContractor(), canAddDocument()
- Enforces freemium rules based on backend limitationsEnabled flag

Screen Updates:
- ContractorsScreen: Show upgrade prompt when contractors limit=0
- DocumentsScreen: Show upgrade prompt when documents limit=0
- ResidencesScreen: Show upgrade prompt when properties limit reached
- ResidenceDetailScreen: Show upgrade prompt when tasks limit reached

UpgradeFeatureScreen:
- Enhanced with feature benefits comparison
- Dynamic content from backend upgrade triggers
- Platform-specific purchase buttons

Additional changes:
- DataCache: Added O(1) lookup maps for ID resolution
- New minimal models (TaskMinimal, ContractorMinimal, ResidenceMinimal)
- TaskApi: Added archive/unarchive endpoints
- Added Google Billing Library dependency
- iOS SubscriptionCache and UpgradePromptView updates

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

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

gradle/libs.versions.toml

@@ -20,6 +20,7 @@ kotlinx-datetime = "0.6.0"
 ktor = "3.3.1"
 firebase-bom = "34.0.0"
 google-services = "4.4.3"
+billing = "7.1.1"
 
 [libraries]
 kotlin-test = { module = "org.jetbrains.kotlin:kotlin-test", version.ref = "kotlin" }
@@ -51,6 +52,7 @@ coil-compose = { module = "io.coil-kt.coil3:coil-compose", version.ref = "coil"
 coil-network-ktor3 = { module = "io.coil-kt.coil3:coil-network-ktor3", version.ref = "coil" }
 firebase-bom = { module = "com.google.firebase:firebase-bom", version.ref = "firebase-bom" }
 firebase-messaging = { module = "com.google.firebase:firebase-messaging-ktx" }
+google-billing = { module = "com.android.billingclient:billing-ktx", version.ref = "billing" }
 
 [plugins]
 androidApplication = { id = "com.android.application", version.ref = "agp" }