Fix error alert infinite loop in ClubsView and ChallengesView (FRE-4664)

- Replace unused lastError state with alertIsPresented boolean
- OK button now clears viewModel.error to prevent re-trigger
- Add onChange observer to show alert when error becomes non-nil
- Applies to both ClubsView.swift and ChallengesView.swift

Co-Authored-By: Paperclip <noreply@paperclip.ing>

Lendair/Views/ChallengesView.swift

@@ -4,7 +4,7 @@ struct ChallengesView: View {
     @StateObject private var viewModel = ChallengeViewModel()
     @State private var showingCreateSheet = false
     @State private var selectedTab: ChallengeTab = .active
-    @State private var lastError: ChallengeError?
+    @State private var alertIsPresented = false
 
     enum ChallengeTab: String, CaseIterable {
         case active, upcoming, completed
@@ -35,11 +35,19 @@ struct ChallengesView: View {
             .sheet(isPresented: $showingCreateSheet) {
                 CreateChallengeSheet(viewModel: viewModel)
             }
-            .alert("Error", isPresented: .init(get: { viewModel.error != nil }, set: { if !$0 { lastError = viewModel.error } })) {
+            .alert("Error", isPresented: $alertIsPresented) {
-                Button("OK") { lastError = viewModel.error }
+                Button("OK") {
+                    viewModel.error = nil
+                    alertIsPresented = false
+                }
             } message: {
                 Text(viewModel.error?.errorDescription ?? "")
             }
+            .onChange(of: viewModel.error) { _ in
+                if viewModel.error != nil {
+                    alertIsPresented = true
+                }
+            }
         }
         .onAppear {
             Task {

Lendair/Views/ClubsView.swift

@@ -4,7 +4,7 @@ struct ClubsView: View {
     @StateObject private var viewModel = ClubViewModel()
     @State private var showingCreateSheet = false
     @State private var selectedTab: ClubTab = .discover
-    @State private var lastError: ClubError?
+    @State private var alertIsPresented = false
 
     enum ClubTab: String, CaseIterable {
         case discover, myClubs
@@ -35,11 +35,19 @@ struct ClubsView: View {
             .sheet(isPresented: $showingCreateSheet) {
                 CreateClubSheet(viewModel: viewModel)
             }
-            .alert("Error", isPresented: .init(get: { viewModel.error != nil }, set: { if !$0 { lastError = nil } })) {
+            .alert("Error", isPresented: $alertIsPresented) {
-                Button("OK") { lastError = viewModel.error }
+                Button("OK") {
+                    viewModel.error = nil
+                    alertIsPresented = false
+                }
             } message: {
                 Text(viewModel.error?.errorDescription ?? "")
             }
+            .onChange(of: viewModel.error) { _ in
+                if viewModel.error != nil {
+                    alertIsPresented = true
+                }
+            }
         }
         .onAppear {
             Task {