Adds a live unread-count signal shared by two navigation-drawer indicators:
- #83: each folder row shows a trailing unread-count badge (capped at
"99+"), hidden when zero. Screen readers announce the exact count via a
plurals content description.
- #84: accounts with unread mail render their email in bold in the drawer
account switcher and the mailbox account-filter chips.
Both derive from one efficient Room aggregate, MessageDao.observeUnreadCounts():
a COUNT(*) ... GROUP BY accountId, folder over folder-synced rows
(inInbox = 1 AND isRead = 0) that pulls no message rows into memory. Its
GROUP BY is served by the existing (accountId, folder, uid) index, so no
schema change or migration is needed. MailboxViewModel derives
folderUnreadCounts (drawer account, per folder) and accountsWithUnread
(any folder) from the one shared flow.
Unread scope is folder-synced mail in any folder, kept consistent across
both features: an account reads as bold exactly when one of its folders
shows a badge.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
JMR-devandClaude Fable 5