feat: add RRULE parsing to shared package and improve ProposedEventCard UI

- Add rrule library to shared package for RRULE string parsing
- Add rruleHelpers.ts with parseRRule() returning freq, until, count, interval, byDay
- Add formatters.ts with German date/time formatters for client and server
- Extend CreateEventDTO with exceptionDates field for proposals
- Extend ChatModel schema with exceptionDates, deleteMode, occurrenceDate
- Update proposeUpdateEvent tool to support isRecurring and recurrenceRule params
- ProposedEventCard now shows green "Neue Ausnahme" and "Neues Ende" text
- Add Sport test scenario with dynamic exception and UNTIL responses
- Update CLAUDE.md documentation

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

@@ -131,7 +131,16 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
         },
         description: {
           type: "string",
-          description: "New description (optional)",
+          description: "New description (optional). NEVER put RRULE here!",
+        },
+        isRecurring: {
+          type: "boolean",
+          description: "Whether this is a recurring event (optional)",
+        },
+        recurrenceRule: {
+          type: "string",
+          description:
+            "RRULE format string (optional). Use to add UNTIL or modify recurrence. Format: FREQ=DAILY;UNTIL=20260310T000000Z",
         },
       },
       required: ["eventId"],