chore: remove test artifacts and cleanup .gitignore

[AniruthKarthik]

• Deleted stemly_app/lib/screens/scan_result_screen.dart.backup
• Deleted backend/test_output.txt and backend/test_image.png
• Fixed corruption in .gitignore and added rules to ignore backup and test files
• Updated ISSUES.md to reflect completed cleanup tasks

[github-actions]

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[SH-Nihil-Mukkesh-25]

Looks good to me! Clean removal of test artifacts, and nice catch fixing the corrupted line in .gitignore.

Minor suggestion for follow-up: test_output.txt and test_image.png rules are very specific - consider broadening to test_output.* or test_*.txt in a future PR. Not a blocker.

Also noting scan_result_screen_fixed.dart (fully commented-out dead file) is another cleanup candidate for a future issue.

Great first contribution @AniruthKarthik! 🎉

[AniruthKarthik]

Minor suggestion for follow-up:
test_output.txt and test_image.png rules are very specific. Consider broadening them to test_output.* or test_*.txt in a future PR. Not a blocker.

The rules are intentionally specific so existing or unrelated test artifacts are not accidentally staged with git add, which keeps diffs clean and avoids committing generated or locally produced files.

Anyways 😀