[Medium] Board flashes a skeleton on every search or filter change #75

Problem

When the user types in search or changes a filter, the board flashes.

Root cause

In src/features/tasks/TasksView.tsx:37-42, each search makes a new queryKey (['tasks', input]). A new key has no data yet, so isPending is true and the whole board is replaced by <TaskBoardSkeleton />.

Proposed fix

Use placeholderData: keepPreviousData in the useQuery, so the old results stay on screen while the new ones load.

Acceptance criteria

• The user types in search and sees the old cards until the new results load, not the skeleton.