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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

config/routes.rb

@@ -53,7 +53,7 @@ Rails.application.routes.draw do
     post :bootstrap, on: :collection
   end
 
-  resources :budgets, only: %i[index show edit update create] do
+  resources :budgets, only: %i[index show edit update], param: :month_year do
     get :picker, on: :collection
 
     resources :budget_categories, only: %i[index show update]
@@ -78,17 +78,18 @@ Rails.application.routes.draw do
 
   resources :accounts, only: %i[index new] do
     collection do
-      get :summary
-      get :list
       post :sync_all
     end
 
     member do
       post :sync
       get :chart
+      get :sparkline
     end
   end
 
+  resources :accountable_sparklines, only: :show, param: :accountable_type
+
   namespace :account do
     resources :holdings, only: %i[index new show destroy]