Add a Material 3 SearchBar overlaying the top of the overview. Collapsed it
is a "Search tasks" bar below the title row; tapping expands it in place to
cover the home content with live results, filtering every task (open and
completed) by title, case-insensitive. The leading icon flips to a back
arrow while expanded, a clear button empties the query, and the FAB hides so
it does not float over the results. Results reuse the upcoming preview row.
ListsViewModel.Content now carries allTasks (open + completed) as the search
corpus; filtering stays in memory so the provider query is untouched.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>