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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -0,0 +1,38 @@
+require "test_helper"
+
+class Account::ChartableTest < ActiveSupport::TestCase
+  test "generates gapfilled balance series" do
+    account = accounts(:depository)
+    account.balances.delete_all
+
+    account.balances.create!(date: 20.days.ago.to_date, balance: 5000, currency: "USD")
+    account.balances.create!(date: 10.days.ago.to_date, balance: 5000, currency: "USD")
+
+    period = Period.last_30_days
+    series = account.balance_series(period: period)
+    assert_equal period.days, series.values.count
+    assert_equal 0, series.values.first.trend.current.amount
+    assert_equal 5000, series.values.find { |v| v.date == 20.days.ago.to_date }.trend.current.amount
+    assert_equal 5000, series.values.find { |v| v.date == 10.days.ago.to_date }.trend.current.amount
+    assert_equal 5000, series.values.last.trend.current.amount
+  end
+
+  test "combines assets and liabilities for multiple accounts properly" do
+    family = families(:empty)
+
+    asset = family.accounts.create!(name: "Asset", currency: "USD", balance: 5000, accountable: Depository.new)
+    liability = family.accounts.create!(name: "Liability", currency: "USD", balance: 2000, accountable: CreditCard.new)
+
+    asset.balances.create!(date: 20.days.ago.to_date, balance: 4000, currency: "USD")
+    asset.balances.create!(date: 10.days.ago.to_date, balance: 5000, currency: "USD")
+
+    liability.balances.create!(date: 20.days.ago.to_date, balance: 1000, currency: "USD")
+    liability.balances.create!(date: 10.days.ago.to_date, balance: 1500, currency: "USD")
+
+    series = family.accounts.balance_series(currency: "USD", period: Period.last_30_days)
+
+    assert_equal 0, series.values.first.trend.current.amount
+    assert_equal 3000, series.values.find { |v| v.date == 20.days.ago.to_date }.trend.current.amount
+    assert_equal 3500, series.values.last.trend.current.amount
+  end
+end