Fix build errors: Self.kXxx refs and MainActor isolation

- Remove leftover Self. prefix on instance storage keys in save()
- Mark TaskViewModel and WorkoutViewModel @MainActor so init() can
  safely access AuthManager.shared without isolation violations

Co-Authored-By: Kutesir <tqwyy79vzn@privaterelay.appleid.com>

KisaniCal/Models/ExerciseModels.swift

@@ -170,6 +170,7 @@ let exerciseSFSymbol: [String: String] = Dictionary(
 )
 
 // MARK: - Workout View Model
+@MainActor
 class WorkoutViewModel: ObservableObject {
     @Published var programs: [WorkoutProgram]
     @Published var schedule: [Int: UUID]
@@ -278,12 +279,12 @@ class WorkoutViewModel: ObservableObject {
 
     private func save() {
         if let data = try? JSONEncoder().encode(programs) {
-            UserDefaults.standard.set(data, forKey: Self.kPrograms)
+            UserDefaults.standard.set(data, forKey: kPrograms)
         }
         let schedDict = schedule.reduce(into: [String: String]()) { $0[String($1.key)] = $1.value.uuidString }
-        UserDefaults.standard.set(schedDict,                  forKey: Self.kSchedule)
-        UserDefaults.standard.set(activeProgramId.uuidString, forKey: Self.kActivePid)
-        UserDefaults.standard.set(workoutDates,               forKey: Self.kWorkoutDates)
+        UserDefaults.standard.set(schedDict,                  forKey: kSchedule)
+        UserDefaults.standard.set(activeProgramId.uuidString, forKey: kActivePid)
+        UserDefaults.standard.set(workoutDates,               forKey: kWorkoutDates)
     }
 
     func logWorkoutCompleted(on date: Date = Date()) {

KisaniCal/Models/TaskItem.swift

@@ -55,6 +55,7 @@ enum TaskColor: String, Codable {
 }
 
 // MARK: - Task View Model
+@MainActor
 class TaskViewModel: ObservableObject {
     @Published var tasks: [TaskItem]