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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

test/lib/money_test.rb

@@ -84,9 +84,10 @@ class MoneyTest < ActiveSupport::TestCase
     assert_not Money.new(-1000).positive?
   end
 
-  test "can cast to string with basic formatting" do
+  test "can format" do
     assert_equal "$1,000.90", Money.new(1000.899).to_s
-    assert_equal "€1.000,12", Money.new(1000.12, :eur).to_s
+    assert_equal "€1,000.12", Money.new(1000.12, :eur).to_s
+    assert_equal "€ 1.000,12", Money.new(1000.12, :eur).format(locale: :nl)
   end
 
   test "converts currency when rate available" do