Introduce IN_PROGRESS as a new task state between TODO and DONE across
the full stack: database enum, Go backend, GraphQL, MCP, and frontend.
The task state icon now cycles forward on click (TODO → IN_PROGRESS →
DONE → TODO), and the action dropdown provides explicit "Move to"
options for any state transition. The "All" tab supports drag-and-drop
between state sections to change a task's state.
Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>
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