feat: add keyboard shortcuts helper modal

[Kokila-chandrakar]

Summary

Implemented a modern keyboard shortcuts helper modal to improve shortcut discoverability and overall editor UX.

Features Added

• Added dedicated keyboard shortcuts modal
• Added keyboard/help icon trigger
• Added responsive modal layout
• Added glassmorphism styling
• Added smooth open/close animations
• Added Esc key close support
• Added accessible dialog semantics

Improvements

• Better discoverability of existing shortcuts
• Cleaner UX compared to collapsible panel
• Consistent dark theme UI

Shortcuts Included

• Export video
• Toggle mute
• Reset settings
• Cancel export
• Preset switching
• Open shortcuts modal

close #910

[vercel]

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[github-actions]

✅ PR Format Check Passed — @Kokila-chandrakar

Basic format checks passed. A maintainer will review your code changes.

This does not mean the PR is approved — it just means the format is correct.

[github-actions]

👋 Thanks for your PR, @Kokila-chandrakar!

Welcome to Reframe — a browser-based video editor built for everyone 🎬

What happens next

1. 🤖 Automated checks — build & TypeScript typecheck will run automatically
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3. 👀 Code review — a maintainer will review your changes
4. 🚀 Merge — once approved, your PR will be merged!

Quick checklist

• PR title follows Conventional Commits (e.g. feat: add dark mode)
• Linked the issue this PR closes (e.g. Closes #123)
• Tested the changes locally (bun run dev)
• Build passes (bun run build)

Useful links

• 📖 CONTRIBUTING.md
• 🐛 Open Issues
• ⭐ Star the repo to support the project!

Happy coding! 🎉