Give share recipients a bell in the web UI

Calendars reached through a share or a group showed a dash instead of a
reminder toggle, in both the sidebar and the settings table, because the
calendar-wide PUT refused a recipient. They now use the dedicated reminders
endpoint, which stores the recipient's own choice, so the toggle is theirs to
make. The comment claiming member-reached group calendars "can't (no PUT)" was
true and is no longer.

The settings table also had its tooltips and the Notifications column header
wired in German while the sidebar next to it went through t(). Moved to a
translation key, added for all ten languages. The remaining headers in that
table are still hardcoded — untouched here, it is a separate job.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/js/i18n.js

@@ -202,6 +202,7 @@ const translations = {
     reminders_calendar_off: 'Für diesen Kalender sind Benachrichtigungen deaktiviert – Erinnerungen werden nicht ausgeführt.',
     calendar_reminders_on: 'Benachrichtigungen aktiviert',
     calendar_reminders_off: 'Benachrichtigungen deaktiviert',
+    calendar_reminders_col: 'Benachrichtigungen',
     copy: 'Kopieren',
     caldav_publish: 'CalDAV veröffentlichen',
     caldav_unpublish: 'CalDAV deaktivieren',
@@ -596,6 +597,7 @@ const translations = {
     reminders_calendar_off: 'Für dä Kalender sind Benachrichtigunge deaktiviert – Erinnerige werded nöd usgfüert.',
     calendar_reminders_on: 'Benachrichtigunge aktiviert',
     calendar_reminders_off: 'Benachrichtigunge deaktiviert',
+    calendar_reminders_col: 'Benachrichtigunge',
     copy: 'Kopierä',
     caldav_publish: 'CalDAV veröffentlichä',
     caldav_unpublish: 'CalDAV deaktivierä',
@@ -1028,6 +1030,7 @@ const translations = {
     reminders_calendar_off: 'Reminders are disabled for this calendar – they will not fire.',
     calendar_reminders_on: 'Reminders enabled',
     calendar_reminders_off: 'Reminders disabled',
+    calendar_reminders_col: 'Notifications',
     copy: 'Copy',
     caldav_publish: 'Publish via CalDAV',
     caldav_unpublish: 'Unpublish CalDAV',
@@ -1422,6 +1425,7 @@ const translations = {
     reminders_calendar_off: 'Les rappels sont désactivés pour cet agenda – ils ne se déclencheront pas.',
     calendar_reminders_on: 'Rappels activés',
     calendar_reminders_off: 'Rappels désactivés',
+    calendar_reminders_col: 'Notifications',
     copy: 'Copier',
     caldav_publish: 'Publier via CalDAV',
     caldav_unpublish: 'Dépublier CalDAV',
@@ -1816,6 +1820,7 @@ const translations = {
     reminders_calendar_off: 'I promemoria sono disattivati per questo calendario – non verranno attivati.',
     calendar_reminders_on: 'Promemoria attivati',
     calendar_reminders_off: 'Promemoria disattivati',
+    calendar_reminders_col: 'Notifiche',
     copy: 'Copia',
     caldav_publish: 'Pubblica via CalDAV',
     caldav_unpublish: 'Annulla pubblicazione CalDAV',
@@ -2210,6 +2215,7 @@ const translations = {
     reminders_calendar_off: 'Herinneringen zijn uitgeschakeld voor deze agenda – ze worden niet geactiveerd.',
     calendar_reminders_on: 'Herinneringen ingeschakeld',
     calendar_reminders_off: 'Herinneringen uitgeschakeld',
+    calendar_reminders_col: 'Meldingen',
     copy: 'Kopiëren',
     caldav_publish: 'Publiceren via CalDAV',
     caldav_unpublish: 'CalDAV-publicatie stoppen',
@@ -2604,6 +2610,7 @@ const translations = {
     reminders_calendar_off: 'Påmindelser er slået fra for denne kalender – de bliver ikke udløst.',
     calendar_reminders_on: 'Påmindelser slået til',
     calendar_reminders_off: 'Påmindelser slået fra',
+    calendar_reminders_col: 'Notifikationer',
     copy: 'Kopiér',
     caldav_publish: 'Udgiv via CalDAV',
     caldav_unpublish: 'Stop CalDAV-udgivelse',
@@ -2998,6 +3005,7 @@ const translations = {
     reminders_calendar_off: 'Påminnelser er slått av for denne kalenderen – de blir ikke utløst.',
     calendar_reminders_on: 'Påminnelser slått på',
     calendar_reminders_off: 'Påminnelser slått av',
+    calendar_reminders_col: 'Varsler',
     copy: 'Kopier',
     caldav_publish: 'Publiser via CalDAV',
     caldav_unpublish: 'Stopp CalDAV-publisering',
@@ -3392,6 +3400,7 @@ const translations = {
     reminders_calendar_off: 'Påminnelser är avstängda för den här kalendern – de kommer inte att utlösas.',
     calendar_reminders_on: 'Påminnelser aktiverade',
     calendar_reminders_off: 'Påminnelser avstängda',
+    calendar_reminders_col: 'Aviseringar',
     copy: 'Kopiera',
     caldav_publish: 'Publicera via CalDAV',
     caldav_unpublish: 'Sluta publicera via CalDAV',
@@ -3786,6 +3795,7 @@ const translations = {
     reminders_calendar_off: 'Muistutukset on poistettu käytöstä tässä kalenterissa – niitä ei laukaista.',
     calendar_reminders_on: 'Muistutukset käytössä',
     calendar_reminders_off: 'Muistutukset pois käytöstä',
+    calendar_reminders_col: 'Ilmoitukset',
     copy: 'Kopioi',
     caldav_publish: 'Julkaise CalDAV:n kautta',
     caldav_unpublish: 'Lopeta CalDAV-julkaisu',