feat(260929-if2): Erinnerungen anlegen und zur Faelligkeit benachrichtigen (Tracer)

- Reminder-Tabelle mit Zeilenschutz (Mandant+Benutzer, Systemlesen fuer den E-Mail-Planer), API reminders (Liste, Anlegen)
- Kachel "Erinnerungen", globaler Melder im Portalrahmen (Browser und Desktop, je Faelligkeit einmal)
- Desktop: Laufzeit-Berechtigung fuer Benachrichtigungen nur fuer die gespeicherte Server-Adresse
- Zugriffsklassifikation nachgemessen

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -476,6 +476,25 @@
       "serversHint": "With nothing selected, the tile shows all servers.",
       "chooseServers": "Choose servers"
     },
+    "reminder": {
+      "name": "Reminders",
+      "description": "Appointments and tasks with a notification at the time you choose",
+      "add": "New reminder",
+      "empty": "No reminders. Create a new reminder.",
+      "formTitle": "New reminder",
+      "dateLabel": "Date",
+      "timeLabel": "Time",
+      "titleLabel": "Title",
+      "descriptionLabel": "Description (optional)",
+      "save": "Save",
+      "cancel": "Cancel",
+      "titleRequired": "Please enter a title.",
+      "pastError": "The chosen time is in the past.",
+      "saveError": "The reminder could not be saved.",
+      "loadError": "Reminders could not be loaded.",
+      "limitReached": "You can have at most 100 reminders.",
+      "notificationTitle": "Reminder: {title}"
+    },
     "editShort": "Edit",
     "done": "Done",
     "toolbarLabel": "Dashboard actions",