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>

Gemfile.saas.lock

@@ -466,7 +466,6 @@ GEM
       erb
       psych (>= 4.0.0)
       tsort
-    redcarpet (3.6.1)
     regexp_parser (2.11.3)
     reline (0.6.3)
       io-console (~> 0.5)
@@ -676,7 +675,6 @@ DEPENDENCIES
   rack-mini-profiler
   rails!
   rails_structured_logging!
-  redcarpet
   rouge
   rqrcode
   rubocop-rails-omakase