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/event-modal.tsx

@@ -729,7 +729,7 @@ export function EventModal({
   }
 
   return (
-    <div ref={modalRef} role="dialog" aria-modal={isMobile || undefined} aria-label={isEdit ? t("events.edit") : t("events.create")} className={isMobile ? "fixed inset-0 z-50 flex flex-col bg-background" : "flex flex-col h-full bg-background"}>
+    <div ref={modalRef} role="dialog" aria-modal={isMobile || undefined} aria-label={isEdit ? t("events.edit") : t("events.create")} data-tour="event-modal" className={isMobile ? "fixed inset-0 z-50 flex flex-col bg-background" : "flex flex-col h-full bg-background"}>
         <div className="flex items-center justify-between px-6 py-4 border-b border-border flex-shrink-0">
           <h2 className="text-lg font-semibold">
             {isEdit ? t("events.edit") : t("events.create")}