Dashboard Member Drill-down per-member metrics and blockers

## Description
Add clickable member cards in the dashboard that expand to show per-member metrics: completed tasks over time, current blockers, skill usage frequency, and recent activity timeline.

## Approach
- Add click handler to member cards in dashboard webview
- Drill-down panel shows: tasks completed (chart), active blockers, skills used, recent log entries
- Reuse existing `SquadDataProvider` methods with per-member filtering
- May require new service methods for skill frequency analysis

## Acceptance Criteria
- [ ] Click on a member card opens a drill-down panel
- [ ] Shows task completion metrics over time
- [ ] Shows current blockers or waiting items
- [ ] Shows skill usage frequency
- [ ] Recent activity timeline from orchestration logs