Introduce lib/ui/widgets/email_tile.dart with an EmailTile widget that
renders a flat email list tile (mail icon, sender, subject, optional
date and location line).
Replace the private _EmailTile class in search_screen.dart and the
inlined ListTile in email_list_screen._buildEmailList() with the shared
widget. Both screens now import EmailTile instead of duplicating the
same sender/subject/icon/date layout.
The widget accepts an optional leading override (for checkbox support
in selection mode) and a showLocation flag (for the global search screen
that appends accountId•mailboxPath under the subject).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
