Add notification badge count and MainTabView with notification tab FRE-4740 FRE-4739

- Add getUnreadCount() endpoint to NotificationsServiceProtocol
- Add NotificationUnreadCountResponse model
- Add badgeCount and fetchUnreadCount() to NotificationsViewModel
- Update markAsRead/markAllAsRead to decrement badge count
- Create MainTabView with Home, Challenges, Clubs, Notifications tabs
- Add unread badge on notification tab using .badge() modifier
- Support injected ViewModel in NotificationsView for shared state
- Add badge count tests to NotificationServiceTests
- Fetch unread count on app launch and tab switch

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

Lendair/Models/Notification.swift

@@ -90,3 +90,7 @@ struct NotificationMarkAllReadResponse: Decodable {
     let success: Bool
     let markedCount: Int
 }
+
+struct NotificationUnreadCountResponse: Decodable {
+    let count: Int
+}

Lendair/Services/NotificationService.swift

@@ -6,6 +6,7 @@ protocol NotificationsServiceProtocol: Sendable {
     func list(params: NotificationListParams) async throws -> [NotificationItem]
     func markAsRead(id: String) async throws
     func markAllAsRead() async throws
+    func getUnreadCount() async throws -> Int
 }
 
 // MARK: - Default Service
@@ -62,6 +63,17 @@ class NotificationsService: NotificationsServiceProtocol {
         _ = try JSONDecoder().decode(NotificationMarkAllReadResponse.self, from: data)
     }
 
+    func getUnreadCount() async throws -> Int {
+        let url = baseURL.appendingPathComponent("/api/notifications/unread-count")
+        let request = try buildRequest(url: url)
+
+        let (data, response) = try await session.data(for: request)
+        try validateResponse(response)
+
+        let decoded = try JSONDecoder().decode(NotificationUnreadCountResponse.self, from: data)
+        return decoded.count
+    }
+
     // MARK: - Helpers
 
     private func buildRequest(url: URL, method: HTTPMethod = .get, body: Data? = nil) throws -> URLRequest {

Lendair/ViewModels/NotificationsViewModel.swift

@@ -5,6 +5,7 @@ import SwiftUI
 class NotificationsViewModel: ObservableObject {
     @Published var notifications: [NotificationItem] = []
     @Published var isLoading: Bool = false
+    @Published var badgeCount: Int = 0
     @Published var lastRefreshDate: Date?
     @Published var error: NotificationError?
 
@@ -25,6 +26,7 @@ class NotificationsViewModel: ObservableObject {
         do {
             let fetchedNotifications = try await notificationsService.list()
             notifications = fetchedNotifications.sorted { $0.createdAt > $1.createdAt }
+            badgeCount = notifications.filter { !$0.isRead }.count
         } catch let error as NotificationError {
             self.error = error
         } catch {
@@ -36,12 +38,22 @@ class NotificationsViewModel: ObservableObject {
         await fetchNotifications()
     }
 
+    func fetchUnreadCount() async {
+        do {
+            let count = try await notificationsService.getUnreadCount()
+            badgeCount = count
+        } catch {
+            print("Failed to fetch unread count: \(error)")
+        }
+    }
+
     func markAsRead(id: String) async {
         guard let index = notifications.firstIndex(where: { $0.id == id }) else { return }
 
         do {
             try await notificationsService.markAsRead(id: id)
             notifications[index].isRead = true
+            badgeCount = max(0, badgeCount - 1)
             objectWillChange.send()
         } catch {
             print("Failed to mark notification as read: \(error)")
@@ -57,6 +69,7 @@ class NotificationsViewModel: ObservableObject {
             for index in notifications.indices {
                 notifications[index].isRead = true
             }
+            badgeCount = 0
             objectWillChange.send()
         } catch {
             print("Failed to mark all as read: \(error)")

Lendair/Views/MainTabView.swift

@@ -0,0 +1,79 @@
+import SwiftUI
+
+struct MainTabView: View {
+    @State private var selectedTab: AppTab = .home
+    @StateObject private var notificationVM = NotificationsViewModel()
+
+    var body: some View {
+        TabView(selection: $selectedTab) {
+            Group {
+                TrainingPlanView()
+                    .tag(AppTab.home)
+                    .tabItem {
+                        Label(AppTab.home.title, systemImage: AppTab.home.icon)
+                    }
+
+                ChallengesView()
+                    .tag(AppTab.challenges)
+                    .tabItem {
+                        Label(AppTab.challenges.title, systemImage: AppTab.challenges.icon)
+                    }
+
+                ClubsView()
+                    .tag(AppTab.clubs)
+                    .tabItem {
+                        Label(AppTab.clubs.title, systemImage: AppTab.clubs.icon)
+                    }
+
+                NotificationsView(viewModel: notificationVM)
+                    .tag(AppTab.notifications)
+                    .tabItem {
+                        Label(AppTab.notifications.title, systemImage: AppTab.notifications.icon)
+                    }
+                    .badge(notificationVM.badgeCount)
+            }
+        }
+        .onAppear {
+            Task {
+                await notificationVM.fetchUnreadCount()
+            }
+        }
+        .onChange(of: selectedTab) { _, newTab in
+            if newTab == .notifications {
+                Task {
+                    await notificationVM.fetchNotifications()
+                    await notificationVM.fetchUnreadCount()
+                }
+            }
+        }
+    }
+}
+
+enum AppTab: String, CaseIterable {
+    case home
+    case challenges
+    case clubs
+    case notifications
+
+    var title: String {
+        switch self {
+        case .home: return "Home"
+        case .challenges: return "Challenges"
+        case .clubs: return "Clubs"
+        case .notifications: return "Notifications"
+        }
+    }
+
+    var icon: String {
+        switch self {
+        case .home: return "house.fill"
+        case .challenges: return "flag.fill"
+        case .clubs: return "person.3.fill"
+        case .notifications: return "bell.fill"
+        }
+    }
+}
+
+#Preview {
+    MainTabView()
+}

Lendair/Views/NotificationsView.swift

@@ -1,8 +1,12 @@
 import SwiftUI
 
 struct NotificationsView: View {
-    @StateObject private var viewModel = NotificationsViewModel()
+    @StateObject private var viewModel: NotificationsViewModel
     @State private var showingRefreshIndicator = false
+
+    init(viewModel: NotificationsViewModel = NotificationsViewModel()) {
+        self._viewModel = StateObject(wrappedValue: viewModel)
+    }
     
     var body: some View {
         NavigationView {