accessibility: add focus restoration to BurnPlanner when modal is closed

[SourabhX16]

Problem Statement

Dismissing BurnPlanner overlay drops keyboard focus to document root.

Why It Matters

Keyboard navigators lose their position in HUD controls.

Expected Behaviour

Restore keyboard focus to trigger button upon panel dismissal.

Acceptance Criteria

• Focus returns to trigger button when BurnPlanner closes.
• Escape key dismisses panel cleanly.
• Focus restoration verified.

Likely Affected Files / Components

• src/components/BurnPlanner.tsx

[prameela9849]

/assign

[github-actions]

✅ Assigned to @prameela9849.

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