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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -7,7 +7,7 @@ class BudgetCategoriesController < ApplicationController
   end
 
   def show
-    @recent_transactions = @budget.entries
+    @recent_transactions = @budget.transactions
 
     if params[:id] == BudgetCategory.uncategorized.id
       @budget_category = @budget.uncategorized_budget_category
@@ -42,6 +42,7 @@ class BudgetCategoriesController < ApplicationController
     end
 
     def set_budget
-      @budget = Current.family.budgets.find(params[:budget_id])
+      start_date = Budget.param_to_date(params[:budget_month_year])
+      @budget = Current.family.budgets.find_by(start_date: start_date)
     end
 end