iOS: localization fixes, per-calendar reminders, widget polish

C1 — Localization: route the remaining hardcoded German strings through
L10n (LoginView, ServerSetupView, SettingsView email, EventDetailSheet) so
"System Default" + English device language shows fully English text.

C2 — Per-calendar reminders: parse the new reminders_enabled flag on every
calendar type; CalendarStore persists a reminderDisabledKeys set and passes
it to NotificationScheduler, which skips events of muted calendars (default
and per-event reminders). Filter sheet gains a per-calendar reminder toggle
(leading swipe + bell.slash indicator), reconciled from the server and
synced back via PUT.

C3 — Widgets:
- Shared WidgetTime.range helper; Today / Today & Tomorrow / Three Days /
  Up Next now show start–end instead of only the start time.
- This Week: show up to 6 events per day (was 3) to use the height.
- Two Weeks: mini event-title pills instead of bare dots.
- Two Months: weeks expand to fill the column (no more empty lower third).
- Day & Events: smaller header/strip/rows so content stops clipping.
- Next 5 days → Next 7 days (range + labels), higher row cap.

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

CalendarrWidgets/UpcomingWidgetView.swift

@@ -4,7 +4,7 @@ import WidgetKit
 private let rowHeight: CGFloat = 16
 private let dayHeaderHeight: CGFloat = 14
 private let maxEventsPerDay: Int = 3
-private let maxTotalRows: Int = 15
+private let maxTotalRows: Int = 22
 
 struct UpcomingWidgetView: View {
     let entry: CalendarrEntry
@@ -16,7 +16,7 @@ struct UpcomingWidgetView: View {
         guard let s = snapshot else { return [] }
         let cal = Calendar.current
         let now = entry.date
-        let events = WidgetHelpers.upcoming(from: now, daysAhead: 5, in: s)
+        let events = WidgetHelpers.upcoming(from: now, daysAhead: 7, in: s)
         var buckets: [Date: [WidgetEvent]] = [:]
         for ev in events {
             let key = cal.startOfDay(for: ev.start)