## Summary
- When viewing an email and then deleting (or archiving/moving/snoozing) it, the app navigates to the next email in the thread list.
- `getEmailBody` fetches from the network on a cache miss, causing the hourglass / loading spinner the issue describes.
- `EmailDetailNotifier` now fires a background `getEmailBody` call for the next thread's `latestEmailId` as soon as the current email finishes loading.
- `getEmailBody` already caches results in the `EmailBodies` table with a 7-day TTL, so by the time the user triggers a navigation action the body is pre-warmed and renders instantly.
## What changed
`lib/di.dart` — `EmailDetailNotifier.build()` calls `_prefetchNextEmailBody` (fire-and-forget via `unawaited`) after loading the current email. The helper respects the `afterMailViewAction` user preference: if set to `showMailbox` it does nothing.
## Test plan
- [ ] Open an email, delete it — next email should appear without the spinner
- [ ] Verify the same for archive, move, and snooze actions
- [ ] Verify behaviour is unchanged when `afterMailViewAction` is set to `showMailbox`
- [ ] Verify the last email in the list still pops back to the mailbox list correctly
Closes#367
Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/381
