New Design System + Codebase Refresh (#1823)

Since the very first 0.1.0-alpha.1 release, we've been moving quickly to add new features to the Maybe app. In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.

Now that "core" Maybe is complete, we're moving into a second phase of development where we'll be working hard to improve the accuracy of existing features and build additional features on top of "core". This PR is a quick overhaul of the existing codebase aimed to:

- Establish the brand new and simplified dashboard view (pictured above)
- Establish and move towards the conventions introduced in Cursor rules and project design overview #1788
- Consolidate layouts and improve the performance of layout queries
- Organize the core models of the Maybe domain (i.e. Account::Entry, Account::Transaction, etc.) and break out specific traits of each model into dedicated concerns for better readability
- Remove stale / dead code from codebase
- Remove overly complex code paths in favor of simpler ones

app/views/mfa/backup_codes.html.erb

@@ -4,7 +4,7 @@
 %>
 
 <% content_for :sidebar do %>
-  <%= render "settings/nav" %>
+  <%= render "settings/settings_nav" %>
 <% end %>
 
 <div class="space-y-4">
@@ -27,4 +27,3 @@
 
   <%= settings_nav_footer %>
 </div>
- 

app/views/mfa/new.html.erb

@@ -4,7 +4,7 @@
 %>
 
 <% content_for :sidebar do %>
-  <%= render "settings/nav" %>
+  <%= render "settings/settings_nav" %>
 <% end %>
 
 <div class="space-y-4">

app/views/mfa/verify.html.erb

@@ -11,4 +11,4 @@
     label: t(".page_title") %>
 
   <%= form.submit t(".verify_button") %>
-<% end %>
+<% end %>