Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

templates/base.html

@@ -20,5 +20,6 @@
       </div>
     </div>
     {% block scripts %}{% endblock %}
+    <script src="/static/js/theme.js"></script>
   </body>
 </html>