Add in-progress state to tasks

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>

pkg/server/api/mcp/v1/specification.yaml

@@ -4615,6 +4615,7 @@ components:
       type: string
       enum:
         - TODO
+        - IN_PROGRESS
         - DONE
       go.probo.inc/mcpgen/type: go.probo.inc/probo/pkg/coredata.TaskState