fix: add export name input

[saurabhhhcodes]

Closes #1282.\n\nAdds a custom export name field in the export settings panel, sanitizes the value for safe filenames, and uses it to seed the final download/share filename.\n\nValidation:\n- node node_modules/typescript/bin/tsc --noEmit\n- node node_modules/vitest/vitest.mjs run src/lib/tests/fileNaming.test.ts\n- git diff --check

[vercel]

Someone is attempting to deploy a commit to the magic-peach1's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

👋 Thanks for your PR, @saurabhhhcodes!

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

What happens next

1. 🤖 Automated checks — build & TypeScript typecheck will run automatically
2. ✅ Vercel preview — a preview deployment will be created (requires maintainer authorization for fork PRs)
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! 🎉

[github-actions]

✅ PR Format Check Passed — @saurabhhhcodes

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.

[magic-peach]

Hi @saurabhhhcodes — thanks for this, and sorry for the wait.

I'd like to get this merged, but it replaces a cn() call with a template literal, which loses Tailwind class-conflict resolution.

To get it unblocked:

1. restore the cn() wrapper on those className props

Could you take a look within the next 14 days? If I don't hear back by then I'll close it to keep the queue manageable — but you're very welcome to reopen it any time after that. Thanks again for contributing to Reframe 🙏