Fix improve UX for back button on workflow bitstream downloads (#4146)

[guillermo-escire]

References

• Fixes Improve UX for back button on workflow bitstream downloads #4146

Description

This PR improves navigation reliability during workflow bitstream downloads by removing the Back button from the bitstream download page.
The button could lead to a Whitelabel error in certain workflow navigation scenarios due to missing or invalid navigation history.

Instructions for Reviewers

This PR removes the Back button from the bitstream download page, as suggested in issue #4146, to ensure consistent and predictable behavior across the UI.

List of changes in this PR:

• Removed the Back button from bitstream-download-page.component.html.
• Removed the unused back() method and related Location dependency from BitstreamDownloadPageComponent.

Include guidance for how to test or review your PR. This may include: steps to reproduce a bug, screenshots or description of a new feature, or reasons behind specific changes.

1. Go to a workflow item page (e.g. /workflowitems/{id}/view).

2. Download a bitstream.

3. Verify that:

   • The download still works as expected.
   • No Back button is displayed on the bitstream download page.
   • Navigation relies on the browser back button, avoiding Whitelabel errors.

4. Confirm that bitstream downloads from the Full Item Page and Admin UI remain unaffected.

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