feat: add recurring event deletion with three modes

Implement three deletion modes for recurring events:
- single: exclude specific occurrence via EXDATE mechanism
- future: set RRULE UNTIL to stop future occurrences
- all: delete entire event series

Changes include:
- Add exceptionDates field to CalendarEvent model
- Add RecurringDeleteMode type and DeleteRecurringEventDTO
- EventService.deleteRecurring() with mode-based logic using rrule library
- EventController DELETE endpoint accepts mode/occurrenceDate query params
- recurrenceExpander filters out exception dates during expansion
- AI tools support deleteMode and occurrenceDate for proposed deletions
- ChatService.confirmEvent() handles recurring delete modes
- New DeleteEventModal component for unified delete confirmation UI
- Calendar screen integrates modal for both recurring and non-recurring events

apps/server/src/ai/utils/toolDefinitions.ts

@@ -140,7 +140,7 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
   {
     name: "proposeDeleteEvent",
     description:
-      "Propose deleting an event. The user must confirm. Use this when the user wants to remove an appointment.",
+      "Propose deleting an event. The user must confirm. Use this when the user wants to remove an appointment. For recurring events, specify deleteMode to control which occurrences to delete.",
     parameters: {
       type: "object",
       properties: {
@@ -148,6 +148,17 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
           type: "string",
           description: "ID of the event to delete",
         },
+        deleteMode: {
+          type: "string",
+          enum: ["single", "future", "all"],
+          description:
+            "For recurring events: 'single' = only this occurrence, 'future' = this and all future, 'all' = entire recurring event. Defaults to 'all' for non-recurring events.",
+        },
+        occurrenceDate: {
+          type: "string",
+          description:
+            "ISO date string (YYYY-MM-DD) of the specific occurrence to delete. Required for 'single' and 'future' modes.",
+        },
       },
       required: ["eventId"],
     },

apps/server/src/ai/utils/toolExecutor.ts

@@ -3,6 +3,7 @@ import {
   getDay,
   Day,
   DAY_TO_GERMAN,
+  RecurringDeleteMode,
 } from "@calchat/shared";
 import { AIContext } from "../../services/interfaces";
 import { formatDate, formatTime, formatDateTime } from "./eventFormatter";
@@ -111,6 +112,8 @@ export function executeToolCall(
 
     case "proposeDeleteEvent": {
       const eventId = args.eventId as string;
+      const deleteMode = (args.deleteMode as RecurringDeleteMode) || "all";
+      const occurrenceDate = args.occurrenceDate as string | undefined;
       const existingEvent = context.existingEvents.find(
         (e) => e.id === eventId,
       );
@@ -119,8 +122,24 @@ export function executeToolCall(
         return { content: `Event mit ID ${eventId} nicht gefunden.` };
       }
 
+      // Build descriptive content based on delete mode
+      let modeDescription = "";
+      if (existingEvent.isRecurring) {
+        switch (deleteMode) {
+          case "single":
+            modeDescription = " (nur dieses Vorkommen)";
+            break;
+          case "future":
+            modeDescription = " (dieses und alle zukünftigen Vorkommen)";
+            break;
+          case "all":
+            modeDescription = " (alle Vorkommen)";
+            break;
+        }
+      }
+
       return {
-        content: `Lösch-Vorschlag für "${existingEvent.title}" erstellt.`,
+        content: `Lösch-Vorschlag für "${existingEvent.title}"${modeDescription} erstellt.`,
         proposedChange: {
           action: "delete",
           eventId,
@@ -131,6 +150,10 @@ export function executeToolCall(
             description: existingEvent.description,
             isRecurring: existingEvent.isRecurring,
           },
+          deleteMode: existingEvent.isRecurring ? deleteMode : undefined,
+          occurrenceDate: existingEvent.isRecurring
+            ? occurrenceDate
+            : undefined,
         },
       };
     }