674d402ff9
Closes #373 ## Summary - **Schema v38**: two new columns on `user_preferences` — `prefetch_mode` (default `wifiOnly`) and `body_cache_limit_mb` (default 100 MB). - **`BodyCacheService`**: queries for emails that have no cached body, fetches them newest-first in batches of 20, and evicts the oldest cached bodies when the configured size limit is exceeded. - **Separate WorkManager task** (`si_bg_prefetch`): runs hourly with `NetworkType.unmetered` (Wi-Fi) or `NetworkType.connected` (any) depending on the user's choice. The task is cancelled when prefetch is disabled. - **App startup**: reads the stored preference from the DB and re-registers the WorkManager task with the correct constraint. - **Preferences screen**: radio group for prefetch mode (Wi-Fi only / Any network / Disabled) and a dropdown for cache size limit (50 / 100 / 200 / 500 MB). ## What is NOT downloaded Binary attachments are never fetched — `getEmailBody()` stores only `textBody` and `htmlBody`. The cache size limit + per-run batch cap (20 emails) keep storage bounded even on large mailboxes. ## Test plan - [x] `task analyze` — no issues - [x] `task test` — all 492 tests pass (incl. updated migration_test.dart for v38) Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de> Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/400