chore: add Prettier formatting validation to frontend PRs

[DevyanshiBansal]

📋 PR Checklist

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🔗 Related Issue

Closes #455

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📝 What does this PR do?

Added a quick workflow to enforce Prettier formatting on the frontend. It automatically checks TS, CSS, and Markdown files on incoming PRs to dev so we don't have to worry about style inconsistencies during code reviews.

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🗂️ Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🔧 Refactor / code cleanup
• 📝 Documentation update
• 🎨 UI / styling change
• [x ] ⚙️ CI / tooling / config change
• 🧪 Tests

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🧪 How was this tested?

• Ran the backend locally (uvicorn app.main:app --reload)
• Ran the frontend locally (npm run dev inside frontend/)
• Tested the affected API endpoints manually
• Added / updated tests
• Note: I verified the YAML syntax and tested the npx prettier --check command locally to ensure it correctly flags unformatted files without altering them.

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📸 Screenshots (if UI change)

N/A

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⚠️ Anything to flag for reviewers?

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✅ Self-Review Checklist

• My branch is based on dev, not main
• I have not added any secrets / API keys
• I have not modified main branch or any HuggingFace deployment config
• My code follows the existing style (no unnecessary formatting changes)
• I have updated relevant docs / comments if needed

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a GitHub Actions workflow to validate Prettier formatting for the frontend on pull requests targeting dev.

Changes:

• Introduces a new workflow triggered on pull_request to dev
• Sets up Node.js 20 and runs a Prettier --check over common frontend file types

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