Web: caret/selection fix, reminder options & labels, group mute, rounded modal

- Stop the blinking text caret / selection on non-editable UI chrome
  (headings, buttons, icons, dropdowns): body is user-select:none, with text
  selection opted back in for inputs/textareas. Felt like an editable field.
- Reminder options trimmed to 5/15/30 min, 1 h, 1 day, 1 week (dropped 10 min,
  2 h, 2 days; added 1 week). Labels now read "5 Minuten vorher", "1 Tag
  vorher", "1 Woche vorher" instead of "vor 5 Min." / "vor 1 Tag(en)".
- Group calendars can now be muted (reminder bell) in the sidebar when owned.
- Event modal corners rounded (20px) to match the pill buttons.
- version v45 -> v46.

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

frontend/js/i18n.js

@@ -97,9 +97,13 @@ const translations = {
     reminders: 'Benachrichtigungen',
     reminder_add: 'Benachrichtigung hinzufügen',
     reminder_at_start: 'Zur Startzeit',
-    reminder_min: 'vor {n} Min.',
-    reminder_hour: 'vor {n} Std.',
-    reminder_day: 'vor {n} Tag(en)',
+    reminder_minutes: '{n} Minuten vorher',
+    reminder_hour_one: '1 Stunde vorher',
+    reminder_hours: '{n} Stunden vorher',
+    reminder_day_one: '1 Tag vorher',
+    reminder_days: '{n} Tage vorher',
+    reminder_week_one: '1 Woche vorher',
+    reminder_weeks: '{n} Wochen vorher',
     calendar_reminders_on: 'Benachrichtigungen aktiviert',
     calendar_reminders_off: 'Benachrichtigungen deaktiviert',
     share: 'Teilen',
@@ -378,9 +382,13 @@ const translations = {
     reminders: 'Reminders',
     reminder_add: 'Add reminder',
     reminder_at_start: 'At start time',
-    reminder_min: '{n} min before',
-    reminder_hour: '{n} h before',
-    reminder_day: '{n} day(s) before',
+    reminder_minutes: '{n} minutes before',
+    reminder_hour_one: '1 hour before',
+    reminder_hours: '{n} hours before',
+    reminder_day_one: '1 day before',
+    reminder_days: '{n} days before',
+    reminder_week_one: '1 week before',
+    reminder_weeks: '{n} weeks before',
     calendar_reminders_on: 'Reminders enabled',
     calendar_reminders_off: 'Reminders disabled',
     share: 'Share',