fix: wrap iOS 17+ APIs in @available checks for iOS 16 compat

ContentUnavailableView and .symbolEffect(.pulse) require iOS 17+
but deployment target is iOS 16. Wrapped all usages in
if #available(iOS 17.0, *) with VStack-based fallbacks for iOS 16.

Files fixed:
- ScanView.swift (4 ContentUnavailableView + 1 symbolEffect)
- QRScannerView.swift (1 ContentUnavailableView)
- BusinessListView.swift (2 ContentUnavailableView)

PayfritBeacon/Views/BusinessListView.swift

@@ -14,6 +14,7 @@ struct BusinessListView: View {
                 if isLoading {
                     ProgressView("Loading businesses…")
                 } else if let error = errorMessage {
+                    if #available(iOS 17.0, *) {
                         ContentUnavailableView {
                             Label("Error", systemImage: "exclamationmark.triangle")
                         } description: {
@@ -21,12 +22,43 @@ struct BusinessListView: View {
                         } actions: {
                             Button("Retry") { Task { await loadBusinesses() } }
                         }
+                    } else {
+                        VStack(spacing: 12) {
+                            Image(systemName: "exclamationmark.triangle")
+                                .font(.system(size: 48))
+                                .foregroundStyle(.orange)
+                            Text("Error")
+                                .font(.headline)
+                            Text(error)
+                                .font(.subheadline)
+                                .foregroundStyle(.secondary)
+                                .multilineTextAlignment(.center)
+                            Button("Retry") { Task { await loadBusinesses() } }
+                                .buttonStyle(.borderedProminent)
+                        }
+                        .padding()
+                    }
                 } else if businesses.isEmpty {
+                    if #available(iOS 17.0, *) {
                         ContentUnavailableView(
                             "No Businesses",
                             systemImage: "building.2",
                             description: Text("You don't have any businesses yet.")
                         )
+                    } else {
+                        VStack(spacing: 12) {
+                            Image(systemName: "building.2")
+                                .font(.system(size: 48))
+                                .foregroundStyle(.secondary)
+                            Text("No Businesses")
+                                .font(.headline)
+                            Text("You don't have any businesses yet.")
+                                .font(.subheadline)
+                                .foregroundStyle(.secondary)
+                        }
+                        .frame(maxHeight: .infinity)
+                        .padding()
+                    }
                 } else {
                     List(businesses) { business in
                         Button {

PayfritBeacon/Views/QRScannerView.swift

@@ -141,7 +141,9 @@ struct QRScannerView: View {
         }
     }
 
+    @ViewBuilder
     private var cameraPermissionDenied: some View {
+        if #available(iOS 17.0, *) {
             ContentUnavailableView {
                 Label("Camera Access Required", systemImage: "camera.fill")
             } description: {
@@ -154,6 +156,26 @@ struct QRScannerView: View {
                 }
                 .buttonStyle(.borderedProminent)
             }
+        } else {
+            VStack(spacing: 16) {
+                Image(systemName: "camera.fill")
+                    .font(.system(size: 48))
+                    .foregroundStyle(.secondary)
+                Text("Camera Access Required")
+                    .font(.headline)
+                Text("Open Settings and enable camera access for Payfrit Beacon.")
+                    .font(.subheadline)
+                    .foregroundStyle(.secondary)
+                    .multilineTextAlignment(.center)
+                Button("Open Settings") {
+                    if let url = URL(string: UIApplication.openSettingsURLString) {
+                        UIApplication.shared.open(url)
+                    }
+                }
+                .buttonStyle(.borderedProminent)
+            }
+            .padding()
+        }
     }
 
     // MARK: - Actions

PayfritBeacon/Views/ScanView.swift

@@ -129,21 +129,40 @@ struct ScanView: View {
         .padding()
     }
 
+    @ViewBuilder
     private var selectServicePointPrompt: some View {
+        if #available(iOS 17.0, *) {
             ContentUnavailableView(
                 "Select a Service Point",
                 systemImage: "mappin.and.ellipse",
                 description: Text("Choose or create a service point (table) to provision a beacon for.")
             )
+        } else {
+            VStack(spacing: 12) {
+                Image(systemName: "mappin.and.ellipse")
+                    .font(.system(size: 48))
+                    .foregroundStyle(.secondary)
+                Text("Select a Service Point")
+                    .font(.headline)
+                Text("Choose or create a service point (table) to provision a beacon for.")
+                    .font(.subheadline)
+                    .foregroundStyle(.secondary)
+                    .multilineTextAlignment(.center)
+            }
+            .frame(maxHeight: .infinity)
+            .padding()
+        }
     }
 
     // MARK: - Namespace Loading
 
+    @ViewBuilder
     private var namespaceLoadingView: some View {
         VStack(spacing: 16) {
             if isLoadingNamespace {
                 ProgressView("Allocating beacon namespace…")
             } else {
+                if #available(iOS 17.0, *) {
                     ContentUnavailableView {
                         Label("Namespace Error", systemImage: "exclamationmark.triangle")
                     } description: {
@@ -151,6 +170,22 @@ struct ScanView: View {
                     } actions: {
                         Button("Retry") { Task { await loadNamespace() } }
                     }
+                } else {
+                    VStack(spacing: 12) {
+                        Image(systemName: "exclamationmark.triangle")
+                            .font(.system(size: 48))
+                            .foregroundStyle(.orange)
+                        Text("Namespace Error")
+                            .font(.headline)
+                        Text(errorMessage ?? "Failed to allocate beacon namespace")
+                            .font(.subheadline)
+                            .foregroundStyle(.secondary)
+                            .multilineTextAlignment(.center)
+                        Button("Retry") { Task { await loadNamespace() } }
+                            .buttonStyle(.borderedProminent)
+                    }
+                    .padding()
+                }
             }
         }
         .frame(maxHeight: .infinity)
@@ -245,11 +280,26 @@ struct ScanView: View {
             .padding()
 
             if bleManager.discoveredBeacons.isEmpty && !bleManager.isScanning {
+                if #available(iOS 17.0, *) {
                     ContentUnavailableView(
                         "No Beacons Found",
                         systemImage: "antenna.radiowaves.left.and.right.slash",
                         description: Text("Tap Scan to search for nearby beacons")
                     )
+                } else {
+                    VStack(spacing: 12) {
+                        Image(systemName: "antenna.radiowaves.left.and.right.slash")
+                            .font(.system(size: 48))
+                            .foregroundStyle(.secondary)
+                        Text("No Beacons Found")
+                            .font(.headline)
+                        Text("Tap Scan to search for nearby beacons")
+                            .font(.subheadline)
+                            .foregroundStyle(.secondary)
+                    }
+                    .frame(maxHeight: .infinity)
+                    .padding()
+                }
             } else {
                 List(bleManager.discoveredBeacons) { beacon in
                     Button {
@@ -274,7 +324,7 @@ struct ScanView: View {
             Image(systemName: "light.beacon.max")
                 .font(.system(size: 64))
                 .foregroundStyle(.orange)
-                .symbolEffect(.pulse)
+                .modifier(PulseEffectModifier())
 
             Text("Beacon is Flashing")
                 .font(.title2.bold())
@@ -768,3 +818,16 @@ struct BeaconRow: View {
     }
 }
 
+// MARK: - iOS 16/17 Compatibility
+
+/// Applies `.symbolEffect(.pulse)` on iOS 17+, no-op on iOS 16
+private struct PulseEffectModifier: ViewModifier {
+    func body(content: Content) -> some View {
+        if #available(iOS 17.0, *) {
+            content.symbolEffect(.pulse)
+        } else {
+            content
+        }
+    }
+}
+