feat(calendar): implement local calendar invitations with email notifications

- Added functionality to create, accept, decline, and delete local calendar invitations.
- Integrated email notifications for calendar event invitations and deletions.
- Updated database schema to support local invitations and outbound event tracking.
- Enhanced the calendar UI to display pending invitations and allow users to manage them.
- Localized new strings for invitations in English and German.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "redlight",
   "private": true,
-  "version": "1.3.0",
+  "version": "1.4.0",
   "type": "module",
   "scripts": {
     "dev": "concurrently -n client,server -c blue,green \"vite\" \"node --watch server/index.js\"",