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/client/src/components/ProposedEventCard.tsx

@@ -1,14 +1,34 @@
 import { View, Text, Pressable } from "react-native";
-import { ProposedEventChange } from "@calchat/shared";
+import { ProposedEventChange, RecurringDeleteMode } from "@calchat/shared";
 import { useThemeStore } from "../stores/ThemeStore";
 import { EventCardBase } from "./EventCardBase";
 
+const DELETE_MODE_LABELS: Record<RecurringDeleteMode, string> = {
+  single: "Nur dieses Vorkommen",
+  future: "Dieses & zukuenftige",
+  all: "Alle Vorkommen",
+};
+
 type ProposedEventCardProps = {
   proposedChange: ProposedEventChange;
   onConfirm: () => void;
   onReject: () => void;
 };
 
+const DeleteModeBadge = ({ mode }: { mode: RecurringDeleteMode }) => {
+  const { theme } = useThemeStore();
+  return (
+    <View
+      className="self-start px-2 py-1 rounded-md mb-2"
+      style={{ backgroundColor: theme.rejectButton }}
+    >
+      <Text style={{ color: theme.buttonText }} className="text-xs font-medium">
+        {DELETE_MODE_LABELS[mode]}
+      </Text>
+    </View>
+  );
+};
+
 const ConfirmRejectButtons = ({
   isDisabled,
   respondedAction,
@@ -68,6 +88,12 @@ export const ProposedEventCard = ({
   // respondedAction is now part of the proposedChange
   const isDisabled = !!proposedChange.respondedAction;
 
+  // Show delete mode badge for delete actions on recurring events
+  const showDeleteModeBadge =
+    proposedChange.action === "delete" &&
+    event?.isRecurring &&
+    proposedChange.deleteMode;
+
   if (!event) {
     return null;
   }
@@ -82,6 +108,9 @@ export const ProposedEventCard = ({
         description={event.description}
         isRecurring={event.isRecurring}
       >
+        {showDeleteModeBadge && (
+          <DeleteModeBadge mode={proposedChange.deleteMode!} />
+        )}
         <ConfirmRejectButtons
           isDisabled={isDisabled}
           respondedAction={proposedChange.respondedAction}