Refactor iOS codebase with SOLID/DRY patterns

Core Infrastructure:
- Add StateFlowObserver for reusable Kotlin StateFlow observation
- Add ValidationRules for centralized form validation
- Add ActionState enum for tracking async operations
- Add KotlinTypeExtensions with .asKotlin helpers
- Add Dependencies factory for dependency injection
- Add ViewState, FormField, and FormState for view layer
- Add LoadingOverlay and AsyncContentView components
- Add form state containers (Task, Residence, Contractor, Document)

ViewModel Updates (9 files):
- Refactor all ViewModels to use StateFlowObserver pattern
- Add optional DI support via initializer parameters
- Reduce boilerplate by ~330 lines across ViewModels

View Updates (4 files):
- Update ResidencesListView to use ListAsyncContentView
- Update ContractorsListView to use ListAsyncContentView
- Update WarrantiesTabContent to use ListAsyncContentView
- Update DocumentsTabContent to use ListAsyncContentView

Net reduction: -332 lines (1007 removed, 675 added)

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

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

iosApp/iosApp/Contractor/ContractorFormSheet.swift

@@ -341,7 +341,7 @@ struct ContractorFormSheet: View {
                 city: city.isEmpty ? nil : city,
                 state: state.isEmpty ? nil : state,
                 zipCode: zipCode.isEmpty ? nil : zipCode,
-                isFavorite: isFavorite.toKotlinBoolean(),
+                isFavorite: isFavorite.asKotlin,
                 isActive: nil,
                 notes: notes.isEmpty ? nil : notes
             )