Render inline code in card titles (#2518)

* Remove unused marked JS dependency

* Remove unused redcarpet dependency

* Render inline code in card titles

Add card_html_title helper that HTML-escapes input then converts
backtick-wrapped text to <code> elements. Apply to card titles in
board preview, card detail, public views, and notification emails.
Style inline code elements in titles to match description styling.

Co-authored-by: Andy Smith <andy@37signals.com>

---------

Co-authored-by: Andy Smith <andy@37signals.com>

app/views/cards/display/_public_preview.html.erb

@@ -17,7 +17,7 @@
     <div class="card__body justify-space-between">
       <div class="card__content">
         <h1 class="card__title overflow-line-clamp">
-          <%= card.title %>
+          <%= card_html_title(card) %>
         </h1>
       </div>