Add tests for Sessions management page. Closes #1277

[chauhan-varun]

Description

I've added unit and integration tests for the Sessions management page to fix the lack of test coverage in this area.

This PR includes:

• Tests for API key management (creating, deleting, and showing/hiding keys).
• Layout tests for the main Sessions page.
• Updated API helper tests.

Related issues

Closes #1277

Type of change

• New feature (non-breaking change which adds functionality).
• Bug fix (non-breaking change which fixes an issue).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Chore (refactoring, dependency updates, CI/CD changes, code cleanup, docs-only changes).

Checklist

Formalities

• I have read and understood the rules about how to Contribute to this project.
• I chose an appropriate title for the pull request in the form: <feature name>. Closes #999
• My branch is based on develop.
• The pull request is for the branch develop.
• I have reviewed and verified any LLM-generated code included in this PR.

Docs and tests

• I documented my code changes with docstrings and/or comments.
• I have checked if my changes affect user-facing behavior that is described in the docs. If so, I also included an update to the wiki in the description of this PR.
• Linter (Ruff) gave 0 errors.
• I have added tests for the feature/bug I solved.
• All the tests gave 0 errors.

GUI changes

• I have created new frontend tests for the new component or updated existing ones.

[chauhan-varun]

Hey @regulartim PTAL