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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -4,11 +4,19 @@ module Monetizable
   class_methods do
     def monetize(*fields)
       fields.each do |field|
-        define_method("#{field}_money") do
-          value = self.send(field)
-          value.nil? ? nil : Money.new(value, currency || Money.default_currency)
+        define_method("#{field}_money") do |**args|
+          value = self.send(field, **args)
+
+          return nil if value.nil? || monetizable_currency.nil?
+
+          Money.new(value, monetizable_currency)
         end
       end
     end
   end
+
+  private
+    def monetizable_currency
+      currency
+    end
 end