Bidirectional Kanban link — moving cards moves tasks

When a planning task is "Sent to a board" via the Kanban hand-off, the card carries metadata pointing back to the planning task. v5 adds the reverse link: when a card moves between lists in Boards, the planning task's status mirrors automatically.

Mapping (case-insensitive, by list name):
• "done" / "complete" / "completed" / "closed" / "shipped" / "finished" → task status `done` (sets % complete = 100)
• "in progress" / "in-progress" / "doing" / "active" / "working" → task status `in_progress` (bumps % to 10 if it was 0)
• "blocked" / "stuck" / "waiting" / "on hold" → task status `blocked`
• Anything else (e.g. "to do", "backlog", "review") → no mirror

Mirror is one-way (board → planning) and only triggers on actual list moves. Editing the card title or description won't touch the planning task. Editing the planning task directly won't override the next move from the board.

This means a delivery team can work entirely in Boards, and the project plan stays correct without anyone re-keying status.