Load the composer, previews, dialogs and other sidebars on demand

The main chunk carried everything the mail view might open: the file
preview and its Markdown renderer, the composer and its editor, the contact
editor, the filter and share dialogs, and the calendar, contacts and files
sidebars. Each is now loaded when first shown. The composer is also
fetched when the browser is idle after startup, so the first Compose does
not wait on the network.

Import the notification helpers statically where they already were: the
dynamic imports beside those static ones split nothing.

web/src/store/mail/index.ts

@@ -28,6 +28,7 @@ import { plural, t } from "@/lib/i18n";
 import { withBase } from "@/lib/basePath";
 import { MAILBOX_PROPS, LIST_PROPS, FULL_PROPS, BODY_PROPS } from "./props";
 import { type ListQuery, type MailState } from "./types";
+import { playNewMailSound, showNotification } from "@/lib/notify/notify";
 
 /*
  * `@/store/mail` stays the one public entry. The split below is about file
@@ -1206,7 +1207,6 @@ async function notifyNewMail(created: Id[], get: () => MailState) {
   const emails = await get().getEmails(created);
   const fresh = emails.filter((e) => e.mailboxIds[inbox] && !e.keywords.$seen && !e.keywords.$draft);
   if (!fresh.length) return;
-  const { showNotification, playNewMailSound } = await import("@/lib/notify/notify");
   if (s.notificationSound) playNewMailSound();
   if (s.desktopNotifications) {
     for (const e of fresh.slice(0, 3)) {