add unit tests for navbar-utils functions handleLogout and deleteAllTasks

[Anujsinghdevx]

Description

Adds unit tests for the handleLogout and deleteAllTasks functions in navbar-utils, covering success, failure, and edge-case scenarios. Ensures proper handling of API responses, task deletion logic, and toast notifications.

-Fixes #352

Checklist

• Ran npx prettier --write . (for formatting)
• 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

No production code was modified; this PR focuses solely on improving test coverage.

[github-actions]

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