Initiales HabitTracker-Projekt: SwiftUI + SwiftData Gewohnheiten-Tracker

Natives iOS-App-Gerüst (Xcode 26, synchronisierte Ordner, iOS 18+).

Features:
- Gewohnheiten anlegen (Name, SF-Symbol, Farbe), heute abhaken, Streaks, Löschen
- Detailansicht mit Monatskalender (Tage nachtragbar) und Statistiken
- Tägliche Erinnerungen via lokale Notifications
- Home-Screen-Widget (klein/mittel) mit App-Group-Datenaustausch

HabitTracker/Support/ModelContext+Habit.swift

@@ -0,0 +1,17 @@
+import Foundation
+import SwiftData
+
+extension ModelContext {
+    /// Toggles completion for a habit on a given day: removes the entry if it
+    /// exists, otherwise inserts one normalized to the start of that day.
+    func toggleCompletion(for habit: Habit, on day: Date) {
+        let calendar = Calendar.current
+        if let entry = habit.entries.first(where: { calendar.isDate($0.date, inSameDayAs: day) }) {
+            delete(entry)
+        } else {
+            let entry = HabitEntry(date: calendar.startOfDay(for: day), habit: habit)
+            insert(entry)
+        }
+        WidgetSync.refresh(self)
+    }
+}

HabitTracker/Support/NotificationManager.swift

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+import Foundation
+import UserNotifications
+
+@MainActor
+enum NotificationManager {
+    /// Default reminder time (09:00) used when the user first enables a reminder.
+    static var defaultTime: Date {
+        Calendar.current.date(bySettingHour: 9, minute: 0, second: 0, of: .now) ?? .now
+    }
+
+    @discardableResult
+    static func requestAuthorization() async -> Bool {
+        do {
+            return try await UNUserNotificationCenter.current()
+                .requestAuthorization(options: [.alert, .sound, .badge])
+        } catch {
+            return false
+        }
+    }
+
+    /// Cancels any existing reminder for the habit and, if it has a reminder
+    /// time, schedules a new daily notification.
+    static func reschedule(for habit: Habit) {
+        let center = UNUserNotificationCenter.current()
+        let id = identifier(for: habit)
+        center.removePendingNotificationRequests(withIdentifiers: [id])
+
+        guard let time = habit.reminderTime else { return }
+
+        let content = UNMutableNotificationContent()
+        content.title = habit.name
+        content.body = "Zeit für deine Gewohnheit"
+        content.sound = .default
+
+        let components = Calendar.current.dateComponents([.hour, .minute], from: time)
+        let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
+        let request = UNNotificationRequest(identifier: id, content: content, trigger: trigger)
+        center.add(request)
+    }
+
+    static func cancel(for habit: Habit) {
+        UNUserNotificationCenter.current()
+            .removePendingNotificationRequests(withIdentifiers: [identifier(for: habit)])
+    }
+
+    private static func identifier(for habit: Habit) -> String {
+        "habit-\(habit.uuid.uuidString)"
+    }
+}

HabitTracker/Support/WidgetSync.swift

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+import Foundation
+import SwiftData
+import WidgetKit
+
+enum WidgetSync {
+    /// Writes the current habits to the shared store and reloads widget timelines.
+    static func refresh(_ context: ModelContext) {
+        let descriptor = FetchDescriptor<Habit>(sortBy: [SortDescriptor(\.createdAt)])
+        let habits = (try? context.fetch(descriptor)) ?? []
+
+        let items = habits.map { habit in
+            WidgetSnapshot.Item(
+                id: habit.uuid,
+                name: habit.name,
+                symbolName: habit.symbolName,
+                colorHex: habit.colorHex,
+                isDoneToday: habit.isCompletedToday
+            )
+        }
+
+        SharedStore.save(WidgetSnapshot(generatedAt: .now, items: items))
+        WidgetCenter.shared.reloadAllTimelines()
+    }
+}