iOS VoiceOver accessibility overhaul — 67 files

New framework:
- AccessibilityLabels.swift: centralized A11y struct with VoiceOver strings
- AccessibilityModifiers.swift: reusable .a11yHeader, .a11yDecorative,
  .a11yButton, .a11yCard, .a11yStatValue View extensions

Shared components: decorative elements hidden, stat views combined,
status/priority badges labeled, error views announced, empty states grouped

Cards: ResidenceCard, TaskCard, DynamicTaskCard, ContractorCard,
DocumentCard, WarrantyCard — all grouped with combined labels,
chevrons hidden, action buttons labeled

Main screens: Login, Register, Residences, Tasks, Contractors, Documents —
toolbar buttons labeled, section headers marked, form field hints added

Onboarding: all 10 views — header traits, button hints, task selection
state, progress indicator, decorative backgrounds hidden

Profile/Subscription: toggle hints, theme selection state, feature
comparison table accessibility, subscription button labels

iOS build verified: BUILD SUCCEEDED

iosApp/iosApp/Onboarding/OnboardingLocationView.swift

@@ -17,6 +17,7 @@ struct OnboardingLocationContent: View {
     var body: some View {
         ZStack {
             WarmGradientBackground()
+                .a11yDecorative()
 
             // Decorative blobs
             GeometryReader { geo in
@@ -54,6 +55,7 @@ struct OnboardingLocationContent: View {
                     .offset(x: geo.size.width * 0.65, y: geo.size.height * 0.75)
                     .blur(radius: 15)
             }
+            .a11yDecorative()
 
             VStack(spacing: 0) {
                 Spacer()
@@ -125,6 +127,7 @@ struct OnboardingLocationContent: View {
                             .font(.system(size: 26, weight: .bold, design: .rounded))
                             .foregroundColor(Color.appTextPrimary)
                             .multilineTextAlignment(.center)
+                            .a11yHeader()
 
                         Text("Enter your ZIP code so we can suggest\nmaintenance tasks for your climate region.")
                             .font(.system(size: 15, weight: .medium))
@@ -163,6 +166,7 @@ struct OnboardingLocationContent: View {
                                 .keyboardType(.numberPad)
                                 .focused($isTextFieldFocused)
                                 .multilineTextAlignment(.center)
+                                .accessibilityHint("Enter your ZIP code")
                                 .onChange(of: zipCode) { _, newValue in
                                     // Only allow digits, max 5
                                     let filtered = String(newValue.filter(\.isNumber).prefix(5))