Render budget images with special chars their names

Images with brackets weren't being rendered properly, so we're now
enclosing the URL in single quotes. In order to render images with
single quotes, we're also using the `j` method.

Since the tests were written by a different developer, we're adding them
in the next commit.

app/components/budgets/budget_component.html.erb

@@ -1,6 +1,6 @@
 <% if budget.image.present? %>
   <div class="budget-header with-background-image"
-       style="background-image: url(<%= polymorphic_path(budget.image.variant(:large)) %>);">
+       style="background-image: url('<%= j polymorphic_path(budget.image.variant(:large)) %>');">
 <% else %>
   <div class="budget-header">
 <% end %>