feat: support multiple event proposals in single AI response

- Change proposedChange to proposedChanges array in ChatMessage type
- Add unique id and individual respondedAction to each ProposedEventChange
- Implement arrow navigation UI for multiple proposals with "Event X von Y" counter
- Add updateProposalResponse() method for per-proposal confirm/reject tracking
- GPTAdapter now collects multiple tool call results into proposals array
- Add RRULE documentation to system prompt (separate events for different times)
- Fix RRULE parsing to strip RRULE: prefix if present
- Add log summarization for large args (conversationHistory, existingEvents)
- Keep proposedChanges logged in full for debugging AI issues

apps/server/src/services/interfaces/ChatRepository.ts

@@ -26,4 +26,10 @@ export interface ChatRepository {
     messageId: string,
     updates: UpdateMessageDTO,
   ): Promise<ChatMessage | null>;
+
+  updateProposalResponse(
+    messageId: string,
+    proposalId: string,
+    respondedAction: "confirm" | "reject",
+  ): Promise<ChatMessage | null>;
 }