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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -6,7 +6,7 @@
   data-controller="tabs"
   data-tabs-active-class="bg-gray-25 text-primary"
   data-tabs-default-tab-value="<%= get_default_transaction_search_filter[:key] %>"
-  class="hidden absolute flex z-10 h-80 w-[540px] top-12 right-0 border border-tertiary bg-white rounded-lg shadow-xs">
+  class="hidden absolute flex z-10 h-80 w-[540px] top-12 right-0 shadow-border-xs bg-white rounded-lg">
   <div class="flex w-44 flex-col items-start p-3 text-sm font-medium text-secondary border-r border-r-alpha-black-100">
     <% transaction_search_filters.each do |filter| %>
       <button