Update export bookmarks endpoint to return file response

[imda-amdlahir]

Description

Update the current export bookmark web-api endpoint to return File Response instead of just the filepath

Motivation and Context

This is for a new feature where user can download the saved bookmarks as json file from the UI

Type of Change

• feat: A new feature

How to Test

[Provide clear instructions on how to test and verify the changes introduced by this pull request, including any specific unit tests you have created to demonstrate your changes.]

Checklist

Please check all the boxes that apply to this pull request using "x":

• [x ] I have tested the changes locally and verified that they work as expected.
• I have added or updated the necessary documentation (README, API docs, etc.).
• I have added appropriate unit tests or functional tests for the changes made.
• [x ] I have followed the project's coding conventions and style guidelines.
• [ x] I have rebased my branch onto the latest commit of the main branch.
• I have squashed or reorganized my commits into logical units.
• I have added any necessary dependencies or packages to the project's build configuration.
• [x ] I have performed a self-review of my own code.
• [x ] I have read, understood and agree to the Developer Certificate of Origin below, which this project utilises.

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Additional Notes

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