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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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/controllers/users_controller.rb

@@ -19,7 +19,10 @@ class UsersController < ApplicationController
       @user.update!(user_params.except(:redirect_to, :delete_profile_image))
       @user.profile_image.purge if should_purge_profile_image?
 
-      handle_redirect(t(".success"))
+      respond_to do |format|
+        format.html { handle_redirect(t(".success")) }
+        format.json { head :ok }
+      end
     end
   end
 
@@ -57,7 +60,7 @@ class UsersController < ApplicationController
 
     def user_params
       params.require(:user).permit(
-        :first_name, :last_name, :email, :profile_image, :redirect_to, :delete_profile_image, :onboarded_at,
+        :first_name, :last_name, :email, :profile_image, :redirect_to, :delete_profile_image, :onboarded_at, :show_sidebar,
         family_attributes: [ :name, :currency, :country, :locale, :date_format, :timezone, :id, :data_enrichment_enabled ]
       )
     end