test: Add comprehensive tests for ExportTasks component

[Hell1213]

Added comprehensive test coverage for ExportTasks component functions that handle task export functionality. Created ExportTasks.test.tsx with 12 test cases covering both JSON and TXT export formats. Tests validate file download mechanics, content formatting, and error handling for empty task scenarios.

Contributes : #299

Checklist

• Ran npx prettier --write . (for formatting)
  -[x] Ran gofmt -w . (for Go backend)
• Ran npm test (for JS/TS testing)
• Added unit tests, if applicable
• Verified all tests pass
• Updated documentation, if needed

Additional Notes
Single test file added with proper browser API mocking for DOM manipulation, URL object creation, and Blob handling. Tests focus on actual export behavior validation without modifying existing functionality. Export features are accessible through navbar dropdown menu.

Screenshots:

[github-actions]

Thank you for opening this PR!

Before a maintainer takes a look, it would be really helpful if you could walk through your changes using GitHub's review tools.

Please take a moment to:

• Check the "Files changed" tab
• Leave comments on any lines for functions, comments, etc. that are important, non-obvious, or may need attention
• Clarify decisions you made or areas you might be unsure about and/or any future updates being considered.
• Finally, submit all the comments!

More information on how to conduct a self review:
https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/reviewing-proposed-changes-in-a-pull-request

This helps make the review process smoother and gives us a clearer understanding of your thought process.

Once you've added your self-review, we'll continue from our side. Thank you!

[Hell1213]

hey @its-me-abhishek ,PR for ExportTasks component is ready plss take a look when you feel free. thanks .!

[Hell1213]

Added test coverage for ExportTasks component by creating ExportTasks.test.tsx file. Tests cover both exportTasksAsJSON and exportTasksAsTXT functions with proper browser API mocking for file downloads. Implementation focuses on validating actual export functionality and error handling for empty task scenarios.