Replaces the dual-sink ($allTasks when residence-scoped is nil,
$tasksByResidence when set) with a single $allTasks observation
that filters in-memory when currentResidenceId is set.
Eliminates the gitea#2 race window where the per-residence cache slot
could be empty while $allTasks was populated, leaving residence
detail stuck on the empty state. After this commit, every emit of
_allTasks rerenders every observing view — kanban tab, residence
detail, dashboards — atomically.
Refs gitea#2
Trey t
882801c71d