feat: event reminders + default reminder setting + local notifications (iOS)

Per-event reminders (multiple, local calendars only) in the editor, prefilled
from a new "default reminder" setting that applies to all events otherwise.
CalEvent gains `reminders`; AppSettings/SettingsSync sync default_reminder_minutes
(always group). New NotificationScheduler requests permission and schedules the
soonest ≤60 upcoming reminders via UNUserNotificationCenter, rescheduling on
load/sync/edit and when the default changes (skipped in group overlay).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Calendarr iOS/Models/AppSettings.swift

@@ -18,6 +18,7 @@ struct AppSettings: Codable {
     var lineColor: String = "#3A3A3C"
     var privateEventVisibility: String = "busy"   // 'hidden' | 'busy'
     var groupVisibleCalendarId: Int? = nil
+    var defaultReminderMinutes: Int? = nil         // minutes before start; nil = off
 
     enum CodingKeys: String, CodingKey {
         case defaultView = "default_view"
@@ -37,6 +38,7 @@ struct AppSettings: Codable {
         case lineColor = "line_color"
         case privateEventVisibility = "private_event_visibility"
         case groupVisibleCalendarId = "group_visible_calendar_id"
+        case defaultReminderMinutes = "default_reminder_minutes"
     }
 
     init() {}
@@ -66,6 +68,7 @@ struct AppSettings: Codable {
         lineColor         = try c.decodeIfPresent(String.self, forKey: .lineColor)         ?? d.lineColor
         privateEventVisibility = try c.decodeIfPresent(String.self, forKey: .privateEventVisibility) ?? d.privateEventVisibility
         groupVisibleCalendarId = try c.decodeIfPresent(Int.self, forKey: .groupVisibleCalendarId)
+        defaultReminderMinutes = try c.decodeIfPresent(Int.self, forKey: .defaultReminderMinutes)
     }
 }
 

Calendarr iOS/Models/CalEvent.swift

@@ -41,6 +41,8 @@ struct CalEvent: Identifiable, Hashable {
     // Server-decorated title for the group combined view (group icon / owner
     // prefix); rendered in group mode while `title` stays raw for editing.
     var displayTitle: String? = nil
+    // Reminder offsets in minutes-before-start (0 = at start). Local events only.
+    var reminders: [Int] = []
 
     // Group view supplies a server-resolved colour; otherwise per-event then calendar colour.
     var effectiveColor: String { displayColor ?? color ?? calendarColor }
@@ -82,7 +84,8 @@ struct CalEvent: Identifiable, Hashable {
             owner: EventPerson.from(json["owner"]),
             isGroupEvent: json["is_group_event"] as? Bool ?? false,
             displayColor: (json["display_color"] as? String).flatMap { $0.isEmpty ? nil : $0 },
-            displayTitle: (json["display_title"] as? String).flatMap { $0.isEmpty ? nil : $0 }
+            displayTitle: (json["display_title"] as? String).flatMap { $0.isEmpty ? nil : $0 },
+            reminders: (json["reminders"] as? [Int]) ?? (json["reminders"] as? [Any])?.compactMap { ($0 as? Int) ?? Int("\($0)") } ?? []
         )
     }
 }

Calendarr iOS/Models/CalendarStore.swift

@@ -264,6 +264,15 @@ class CalendarStore {
             return !hiddenCalendarKeys.contains(key)
                 && !banishedCalendarKeys.contains(key)
         }
+        // Personal events drive local reminder notifications.
+        NotificationScheduler.reschedule(events: allCachedEvents)
+    }
+
+    /// Recompute scheduled reminder notifications from the personal cache
+    /// (skipped while a group overlay is active).
+    func rescheduleNotifications() {
+        guard activeGroup == nil else { return }
+        NotificationScheduler.reschedule(events: allCachedEvents)
     }
 
     /// Optimistically drop a just-deleted event from the cache so it disappears

Calendarr iOS/Models/ReminderOptions.swift

@@ -0,0 +1,37 @@
+import Foundation
+
+/// Reminder offset options (minutes before an event's start; 0 = at start) and
+/// their localized labels. Shared by the event editor, the settings default
+/// picker, and the notification scheduler so the choices stay consistent.
+enum ReminderOptions {
+    /// Selectable offsets in minutes-before-start.
+    static let all: [Int] = [0, 5, 10, 15, 30, 60, 120, 1440, 2880]
+
+    private static func isEnglish(_ appLang: String) -> Bool {
+        if appLang == "en" { return true }
+        if appLang == "de" { return false }
+        return (Locale.current.language.languageCode?.identifier ?? "de").hasPrefix("en")
+    }
+
+    static func label(_ minutes: Int, _ appLang: String) -> String {
+        let en = isEnglish(appLang)
+        if minutes <= 0 { return en ? "At start time" : "Zur Startzeit" }
+        if minutes < 60 { return en ? "\(minutes) min before" : "\(minutes) Min. vorher" }
+        if minutes < 1440 {
+            let h = minutes / 60
+            return en ? "\(h) h before" : "\(h) Std. vorher"
+        }
+        let d = minutes / 1440
+        return en ? "\(d) day\(d == 1 ? "" : "s") before" : "\(d) Tag\(d == 1 ? "" : "e") vorher"
+    }
+
+    static func sectionTitle(_ l: String) -> String { isEnglish(l) ? "Reminders" : "Benachrichtigungen" }
+    static func addLabel(_ l: String) -> String { isEnglish(l) ? "Add reminder" : "Benachrichtigung hinzufügen" }
+    static func off(_ l: String) -> String { isEnglish(l) ? "Off" : "Aus" }
+    static func defaultTitle(_ l: String) -> String { isEnglish(l) ? "Default reminder" : "Standardbenachrichtigung" }
+    static func defaultFooter(_ l: String) -> String {
+        isEnglish(l)
+            ? "Applies to all events unless an event has its own reminders."
+            : "Gilt für alle Termine, sofern ein Termin keine eigenen Benachrichtigungen hat."
+    }
+}