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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -115,12 +115,6 @@ class PlaidAccount < ApplicationRecord
       plaid_item.family
     end
 
-    def transfer?(plaid_txn)
-      transfer_categories = [ "TRANSFER_IN", "TRANSFER_OUT", "LOAN_PAYMENTS" ]
-
-      transfer_categories.include?(plaid_txn.personal_finance_category.primary)
-    end
-
     def create_initial_loan_balance(loan_data)
       if loan_data.origination_principal_amount.present? && loan_data.origination_date.present?
         account.entries.find_or_create_by!(plaid_id: loan_data.account_id) do |e|