feat: Kanban smart recommendations + board health score

Analyzes board state and surfaces actionable insights:

Workflow: WIP limits, review bottlenecks, done archival
Hygiene: missing labels/descriptions, stale cards, priority misplacement
Productivity: empty board, deadline coverage, subtask progress
Suggestions: rotating tips (shortcuts, labels, time tracking)

Board Health Score: WIP control, label/description coverage, freshness, on-time %
Actions: highlight columns, open cards, create cards, clear done, toast tips
Persistent: dismissed recs + panel state in localStorage

Author: BunsDev