feat: add data-testid attributes to key UI elements

[Youngmaster0304]

What this does

Added data-testid attributes to key UI elements for automated testing.

Why

data-testid attributes allow Playwright or React Testing Library to reliably select elements without depending on CSS classes or text content.

Changes

• file-upload-zone: File upload drop zone
• export-button: Export video button
• export-progress: Progress bar during export
• download-button: Download result button
• reset-button: Reset/upload new video button
• quality-slider: Quality CRF slider
• speed-slider: Speed control slider

Acceptance Criteria

• All listed elements have data-testid attributes
• No visual or functional changes

Contributor

Abhinav Jha (@Youngmaster0304) | abhinavjha0304@gmail.com
GSSoC 2026 Participant

Fixes #56

[vercel]

@Youngmaster0304 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]

✅ PR Format Check Passed — @Youngmaster0304

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, @Youngmaster0304!

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

🟠 GSSoC'26 PR detected — thanks for contributing under GirlScript Summer of Code 2026!

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! 🎉

[magic-peach]

Thanks for the contribution! Another open PR (#1741: feat: add data-testid attributes to key UI elements for automated testing) tackles the same issue and is a bit further along (cleaner CI / no merge conflicts), so I'm consolidating there to keep review focused in one place. Closing this one — no reflection on the work itself, just avoiding split review across duplicates. Feel free to bring anything over to #1741 if it adds something that one doesn't have yet!