Fix and simplify integration of custom detail dialogs and event bars for calendar events

.../frontend/components/calendar/BaseCalendarFeedDetails.vue

...frontend/components/calendar/BaseCalendarFeedEventBar.vue

...is/core/frontend/components/calendar/CalendarOverview.vue

...ontend/components/calendar/GenericCalendarFeedDetails.vue

...ntend/components/calendar/GenericCalendarFeedEventBar.vue

...nd/components/calendar_feeds/details/BirthdaysDetails.vue

...components/calendar_feeds/event_bar/BirthdaysEventBar.vue

aleksis/core/frontend/mixins/calendarFeedDetails.js

aleksis/core/frontend/mixins/calendarFeedEventBar.js

aleksis/core/vite.config.js