feat(a11y): add keyboard navigation to goal cards

[Mahesh-forcode]

Summary

Add keyboard navigation to goal cards so keyboard-only users can Tab to each card and interact with Enter/Space.

Closes #2251

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Type of Change

• 🐛 Bug fix
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change
• 📝 Documentation update
• ♻️ Refactor / code cleanup
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• src/components/GoalTracker.tsx: Added tabIndex={0} to each goal card <li> to make it focusable via Tab
• src/components/GoalTracker.tsx: Added onKeyDown handler — Enter/Space triggers the first interactive button inside the card
• src/components/GoalTracker.tsx: Added focus-visible:ring-2 focus-visible:ring-[var(--accent)] for visible focus indicator
• src/components/GoalTracker.tsx: Added aria-label announcing goal title, progress, and status to screen readers

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How to Test

1. Open the dashboard and go to the Goal Tracker section
2. Press Tab until a goal card is focused
3. Press Enter or Space on the focused card

Expected result: Card receives a visible accent-colored ring on focus. Enter/Space triggers the primary button (+1 for manual goals, delete for auto-synced goals). Mouse behavior is unchanged.

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log, debug code, or commented-out blocks
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Added or updated tests where applicable
• Updated documentation / comments if behavior changed

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Accessibility (UI changes only)

• Keyboard navigation works correctly
• Color contrast meets WCAG AA standard
• ARIA labels / roles added where needed
• Tested on mobile / responsive layout

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Additional Context

Only GoalTracker.tsx was modified. No visual changes for mouse/touch users. Implements WCAG 2.1 Level A — 2.1.1 Keyboard requirement.

[github-actions]

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