Implement unified network layer with APILayer and migrate iOS ViewModels

Major architectural improvements:
- Created APILayer as single entry point for all network operations
- Integrated cache-first reads with automatic cache updates on mutations
- Migrated all shared Kotlin ViewModels to use APILayer instead of direct API calls
- Migrated iOS ViewModels to wrap shared Kotlin ViewModels with StateFlow observation
- Replaced LookupsManager with DataCache for centralized lookup data management
- Added password reset methods to AuthViewModel
- Added task completion and update methods to APILayer
- Added residence user management methods to APILayer

iOS specific changes:
- Updated LoginViewModel, RegisterViewModel, ProfileViewModel to use shared AuthViewModel
- Updated ContractorViewModel, DocumentViewModel to use shared ViewModels
- Updated ResidenceViewModel to use shared ViewModel and APILayer
- Updated TaskViewModel to wrap shared ViewModel with callback-based interface
- Migrated PasswordResetViewModel and VerifyEmailViewModel to shared AuthViewModel
- Migrated AllTasksView, CompleteTaskView, EditTaskView to use APILayer
- Migrated ManageUsersView, ResidenceDetailView to use APILayer
- Migrated JoinResidenceView to use async/await pattern with APILayer
- Removed LookupsManager.swift in favor of DataCache
- Fixed PushNotificationManager @MainActor issue
- Converted all direct API calls to use async/await with proper error handling

Benefits:
- Reduced code duplication between iOS and Android
- Consistent error handling across platforms
- Automatic cache management for better performance
- Centralized network layer for easier testing and maintenance
- Net reduction of ~700 lines of code through shared logic

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

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

iosApp/iosApp/Contractor/ContractorFormSheet.swift

@@ -4,7 +4,6 @@ import ComposeApp
 struct ContractorFormSheet: View {
     @Environment(\.dismiss) private var dismiss
     @StateObject private var viewModel = ContractorViewModel()
-    @ObservedObject private var lookupsManager = LookupsManager.shared
 
     let contractor: Contractor?
     let onSave: () -> Void
@@ -28,8 +27,11 @@ struct ContractorFormSheet: View {
     @State private var showingSpecialtyPicker = false
     @FocusState private var focusedField: Field?
 
+    // Lookups from DataCache
+    @State private var contractorSpecialties: [ContractorSpecialty] = []
+
     var specialties: [String] {
-        lookupsManager.contractorSpecialties.map { $0.name }
+        contractorSpecialties.map { $0.name }
     }
 
     enum Field: Hashable {
@@ -258,7 +260,7 @@ struct ContractorFormSheet: View {
             }
             .onAppear {
                 loadContractorData()
-                lookupsManager.loadContractorSpecialties()
+                loadContractorSpecialties()
             }
         }
     }
@@ -286,6 +288,14 @@ struct ContractorFormSheet: View {
         isFavorite = contractor.isFavorite
     }
 
+    private func loadContractorSpecialties() {
+        Task {
+            await MainActor.run {
+                self.contractorSpecialties = DataCache.shared.contractorSpecialties.value as! [ContractorSpecialty]
+            }
+        }
+    }
+
     private func saveContractor() {
         if let contractor = contractor {
             // Update existing contractor