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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -7,7 +7,7 @@
 
   <div class="flex items-start gap-4">
     <div class="w-[300px] space-y-4">
-      <div class="h-[300px] bg-white rounded-xl shadow-xs p-8 border border-gray-100">
+      <div class="h-[300px] bg-white rounded-xl shadow-border-xs p-8">
         <% if @budget.available_to_allocate.negative? %>
           <%= render "budgets/over_allocation_warning", budget: @budget %>
         <% else %>
@@ -38,18 +38,18 @@
                         ) %>
           </div>
 
-          <div class="bg-white rounded-xl shadow-xs border border-gray-100">
+          <div class="bg-white rounded-xl shadow-border-xs">
             <%= render selected_tab == "budgeted" ? "budgets/budgeted_summary" : "budgets/actuals_summary", budget: @budget %>
           </div>
         <% else %>
-          <div class="bg-white rounded-xl shadow-xs border border-gray-100">
+          <div class="bg-white rounded-xl shadow-border-xs">
             <%= render "budgets/actuals_summary", budget: @budget %>
           </div>
         <% end %>
       </div>
     </div>
 
-    <div class="grow bg-white rounded-xl shadow-xs p-4 border border-gray-100">
+    <div class="grow bg-white rounded-xl shadow-border-xs p-4">
       <div class="flex items-center justify-between mb-4">
         <h2 class="text-lg font-medium">Categories</h2>