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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -0,0 +1,48 @@
+require "test_helper"
+
+class IncomeStatementTest < ActiveSupport::TestCase
+  include Account::EntriesTestHelper
+
+  setup do
+    @family = families(:empty)
+
+    @income_category = @family.categories.create! name: "Income", classification: "income"
+    @food_category = @family.categories.create! name: "Food", classification: "expense"
+    @shopping_category = @family.categories.create! name: "Shopping", classification: "expense", parent: @food_category
+
+    @checking_account = @family.accounts.create! name: "Checking", currency: @family.currency, balance: 5000, accountable: Depository.new
+    @credit_card_account = @family.accounts.create! name: "Credit Card", currency: @family.currency, balance: 1000, accountable: CreditCard.new
+
+    create_transaction(account: @checking_account, amount: -1000, category: @food_category)
+    create_transaction(account: @checking_account, amount: 200, category: @shopping_category)
+    create_transaction(account: @credit_card_account, amount: 300, category: @food_category)
+    create_transaction(account: @credit_card_account, amount: 400, category: @shopping_category)
+  end
+
+  test "calculates totals for transactions" do
+    income_statement = IncomeStatement.new(@family)
+    assert_equal Money.new(1000, @family.currency), income_statement.totals.income_money
+    assert_equal Money.new(200 + 300 + 400, @family.currency), income_statement.totals.expense_money
+    assert_equal 4, income_statement.totals.transactions_count
+  end
+
+  test "calculates expenses for a period" do
+    income_statement = IncomeStatement.new(@family)
+    assert_equal 200 + 300 + 400, income_statement.expense_totals(period: Period.last_30_days).total
+  end
+
+  test "calculates income for a period" do
+    income_statement = IncomeStatement.new(@family)
+    assert_equal 1000, income_statement.income_totals(period: Period.last_30_days).total
+  end
+
+  test "calculates median expense" do
+    income_statement = IncomeStatement.new(@family)
+    assert_equal 200 + 300 + 400, income_statement.expense_totals(period: Period.last_30_days).total
+  end
+
+  test "calculates median income" do
+    income_statement = IncomeStatement.new(@family)
+    assert_equal 1000, income_statement.income_totals(period: Period.last_30_days).total
+  end
+end