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.

app/[locale]/calendar/page.tsx

@@ -795,6 +795,7 @@ export default function CalendarPage() {
 
         <div
           className="flex flex-1 overflow-hidden relative"
+          data-tour="calendar-view"
           onTouchStart={handleTouchStart}
           onTouchEnd={handleTouchEnd}
         >