Apply suggestions from code review

Operator precedence clarity & fixes etc.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: fbacall

app/assets/stylesheets/application.scss

@@ -1076,7 +1076,7 @@ td.day .calendar-text {
 
 .theme-selector {
   display: flex;
-  gap: 10px
+  gap: 10px;
 }
 
 .theme-select-option {

app/policies/content_provider_policy.rb

@@ -1,6 +1,6 @@
 class ContentProviderPolicy < ScrapedResourcePolicy
   def create_source?
-    TeSS::Config.feature['user_source_creation'] && manage? ||
+    (TeSS::Config.feature['user_source_creation'] && manage?) ||
       user_has_role?(:admin, :curator)
   end
 end

app/policies/source_policy.rb

@@ -27,7 +27,7 @@ def request_approval?
   private
 
   def administration? # Can edit sources for any content provider
-    curators_and_admin || user_has_role?(:admin)
+    curators_and_admin
   end
 
   def user_management?

app/views/layouts/_user_menu.html.erb

@@ -40,7 +40,7 @@
         </li>
       <% end %>
 
-      <% if !TeSS::Config.feature['disabled'].include?('topics') && is_admin || is_curator %>
+      <% if !TeSS::Config.feature['disabled'].include?('topics') && (is_admin || is_curator) %>
         <li class="dropdown-item">
           <%= link_to curate_topic_suggestions_path,
                       title: t('menu.user.assign_scientific_topics',