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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -1,34 +1,26 @@
 class TransactionsController < ApplicationController
   include ScrollFocusable
 
-  layout :with_sidebar
-
   before_action :store_params!, only: :index
 
   def index
     @q = search_params
-    search_query = Current.family.transactions.search(@q).active
+    transactions_query = Current.family.transactions.active.search(@q)
 
-    set_focused_record(search_query, params[:focused_record_id], default_per_page: 50)
+    set_focused_record(transactions_query, params[:focused_record_id], default_per_page: 50)
 
-    @pagy, @transaction_entries = pagy(
-      search_query.reverse_chronological.preload(
-        :account,
-        entryable: [
-          :category, :merchant, :tags,
-          :transfer_as_inflow,
-          transfer_as_outflow: {
-            inflow_transaction: { entry: :account },
-            outflow_transaction: { entry: :account }
-          }
-        ]
-      ),
+    @pagy, @transactions = pagy(
+      transactions_query.includes(
+        { entry: :account },
+        :category, :merchant, :tags,
+        transfer_as_outflow: { inflow_transaction: { entry: :account } },
+        transfer_as_inflow: { outflow_transaction: { entry: :account } }
+      ).reverse_chronological,
       limit: params[:per_page].presence || default_params[:per_page],
       params: ->(params) { params.except(:focused_record_id) }
     )
 
-    @transfers = @transaction_entries.map { |entry| entry.entryable.transfer_as_outflow }.compact
-    @totals = search_query.stats(Current.family.currency)
+    @totals = Current.family.income_statement.totals(transactions_scope: transactions_query)
   end
 
   def clear_filter