feat: add demo data for emails, files, filters, identities, mailboxes, vacation responses, and JMAP client interface

- Created demo emails with various states (inbox, sent, drafts, trash, etc.) in `emails.ts`.
- Added demo file nodes representing directories and files in `files.ts`.
- Implemented demo Sieve capabilities and scripts in `filters.ts`.
- Defined demo identities for users in `identities.ts`.
- Established demo mailboxes with permissions and counts in `mailboxes.ts`.
- Created a demo vacation response in `vacation.ts`.
- Introduced a comprehensive JMAP client interface in `client-interface.ts` to standardize interactions with the JMAP API.

components/calendar/ical-subscription-modal.tsx

@@ -4,13 +4,13 @@ import { useState, useRef, useEffect, useCallback } from "react";
 import { useTranslations } from "next-intl";
 import { Button } from "@/components/ui/button";
 import { X, Loader2, Globe } from "lucide-react";
-import type { JMAPClient } from "@/lib/jmap/client";
+import type { IJMAPClient } from '@/lib/jmap/client-interface';
 import { useCalendarStore } from "@/stores/calendar-store";
 import { CalendarColorPicker } from "@/components/settings/calendar-management-settings";
 import { toast } from "@/stores/toast-store";
 
 interface ICalSubscriptionModalProps {
-  client: JMAPClient;
+  client: IJMAPClient;
   onClose: () => void;
 }