Add task persistence and per-task reminder notifications

Tasks now survive app restarts via UserDefaults JSON. Each task with a
due time fires a notification at that exact time; date-only tasks fire
at 9am on the due date. Completing or deleting a task cancels its
pending notification. ContentView now reschedules on any task change.

KisaniCal/Models/TaskItem.swift

@@ -1,10 +1,11 @@
 import SwiftUI
 
 // MARK: - Task Model
-struct TaskItem: Identifiable {
+struct TaskItem: Identifiable, Codable, Equatable {
     var id = UUID()
     var title: String
     var dueDate: Date?
+    var hasTime: Bool = false
     var isComplete: Bool = false
     var completedAt: Date? = nil
     var quadrant: Quadrant = .urgent
@@ -13,7 +14,7 @@ struct TaskItem: Identifiable {
     var isRecurring: Bool = false
 }
 
-enum Quadrant: String, CaseIterable, Identifiable {
+enum Quadrant: String, CaseIterable, Identifiable, Codable {
     var id: String { rawValue }
     case urgent    = "Urgent + Important"
     case schedule  = "Schedule It"
@@ -21,7 +22,7 @@ enum Quadrant: String, CaseIterable, Identifiable {
     case eliminate = "Eliminate"
 }
 
-enum TaskCategory: String {
+enum TaskCategory: String, Codable {
     case reminder = "Reminder"
     case birthday = "Birthday"
     case domain   = "Domain"
@@ -29,7 +30,7 @@ enum TaskCategory: String {
     case custom   = "Custom"
 }
 
-enum TaskColor {
+enum TaskColor: String, Codable {
     case orange, green, blue, yellow
 
     func color() -> Color {
@@ -52,7 +53,24 @@ enum TaskColor {
 
 // MARK: - Task View Model
 class TaskViewModel: ObservableObject {
-    @Published var tasks: [TaskItem] = sampleTasks
+    @Published var tasks: [TaskItem]
+
+    private static let persistKey = "kisani.tasks.v2"
+
+    init() {
+        if let data = UserDefaults.standard.data(forKey: Self.persistKey),
+           let saved = try? JSONDecoder().decode([TaskItem].self, from: data), !saved.isEmpty {
+            tasks = saved
+        } else {
+            tasks = sampleTasks
+        }
+    }
+
+    private func save() {
+        if let data = try? JSONEncoder().encode(tasks) {
+            UserDefaults.standard.set(data, forKey: Self.persistKey)
+        }
+    }
 
     var overdueTasks: [TaskItem] {
         let startOfDay = Calendar.current.startOfDay(for: Date())
@@ -83,22 +101,26 @@ class TaskViewModel: ObservableObject {
         guard let idx = tasks.firstIndex(where: { $0.id == task.id }) else { return }
         tasks[idx].isComplete.toggle()
         tasks[idx].completedAt = tasks[idx].isComplete ? Date() : nil
+        save()
     }
     func tasks(for quadrant: Quadrant) -> [TaskItem] {
         tasks.filter { $0.quadrant == quadrant }
     }
 
-    func addTask(title: String, dueDate: Date?, quadrant: Quadrant = .urgent,
-                 category: TaskCategory = .reminder, taskColor: TaskColor = .orange,
-                 isRecurring: Bool = false) {
-        tasks.append(TaskItem(title: title, dueDate: dueDate, quadrant: quadrant,
-                              category: category, taskColor: taskColor, isRecurring: isRecurring))
+    func addTask(title: String, dueDate: Date?, hasTime: Bool = false,
+                 quadrant: Quadrant = .urgent, category: TaskCategory = .reminder,
+                 taskColor: TaskColor = .orange, isRecurring: Bool = false) {
+        tasks.append(TaskItem(title: title, dueDate: dueDate, hasTime: hasTime,
+                              quadrant: quadrant, category: category,
+                              taskColor: taskColor, isRecurring: isRecurring))
+        save()
     }
 
     func postpone(_ task: TaskItem, days: Int = 1) {
         guard let idx = tasks.firstIndex(where: { $0.id == task.id }) else { return }
         let base = tasks[idx].dueDate ?? Date()
         tasks[idx].dueDate = Calendar.current.date(byAdding: .day, value: days, to: base)
+        save()
     }
 
     func postponeAllOverdue(days: Int = 1) {
@@ -108,10 +130,12 @@ class TaskViewModel: ObservableObject {
             let base = tasks[idx].dueDate ?? Date()
             tasks[idx].dueDate = Calendar.current.date(byAdding: .day, value: days, to: base)
         }
+        save()
     }
 
     func delete(_ task: TaskItem) {
         tasks.removeAll { $0.id == task.id }
+        save()
     }
 }