feat(shortcuts): add useKeyboardShortcuts hook, time range keys (1-4)…

[Nareshkumawat-star]

Summary

Adds developer-first keyboard shortcuts to DevTrack, including time-range switching (1 → 7d, 2 → 14d, 3 → 30d, 4 → 90d), data refresh (R), modal help toggle (? or Cmd+/), and modal close (Escape). Introduces a reusable useKeyboardShortcuts hook in src/lib/ and updates ShortcutsModal.tsx.

Closes #3247

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• src/lib/useKeyboardShortcuts.ts: Custom hook managing keyboard listeners with focus checks (input, textarea, select, contenteditable).
• src/components/GlobalKeyboardShortcuts.tsx: Wired range keys 1–4, R refresh, Cmd+/ / ? help toggle, and Escape.
• src/components/ShortcutsModal.tsx: Updated shortcut key legend UI to display range keys and Cmd+/.

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How to Test

1. Open the DevTrack dashboard.
2. Press 1, 2, 3, or 4 to switch dashboard time ranges (7d, 14d, 30d, 90d).
3. Press ? or Cmd+/ (Ctrl+/ on Windows) to open the Keyboard Shortcuts modal.
4. Press Escape to close the modal.
5. Click into an input box (e.g. search) and press 1 or R — verify shortcuts do not trigger while typing.

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Checklist

• Self-reviewed my own diff
• No unnecessary console.log or debug code
• Keyboard focus isolation in form inputs verified
• ARIA modal & focus trap standards maintained

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

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[Nareshkumawat-star]

Hi @Priyanshu-byte-coder kindly review and merge it