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 In doing so, some parts of the codebase have become outdated, unnecessary, or overly-complex as a natural result of this feature prioritization.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

@@ -0,0 +1,40 @@
+module Account::Transaction::Transferable
+  extend ActiveSupport::Concern
+
+  included do
+    has_one :transfer_as_inflow, class_name: "Transfer", foreign_key: "inflow_transaction_id", dependent: :destroy
+    has_one :transfer_as_outflow, class_name: "Transfer", foreign_key: "outflow_transaction_id", dependent: :destroy
+
+    # We keep track of rejected transfers to avoid auto-matching them again
+    has_one :rejected_transfer_as_inflow, class_name: "RejectedTransfer", foreign_key: "inflow_transaction_id", dependent: :destroy
+    has_one :rejected_transfer_as_outflow, class_name: "RejectedTransfer", foreign_key: "outflow_transaction_id", dependent: :destroy
+  end
+
+  def transfer
+    transfer_as_inflow || transfer_as_outflow
+  end
+
+  def transfer?
+    transfer.present?
+  end
+
+  def transfer_match_candidates
+    candidates_scope = if self.entry.amount.negative?
+      family_matches_scope.where("inflow_candidates.entryable_id = ?", self.id)
+    else
+      family_matches_scope.where("outflow_candidates.entryable_id = ?", self.id)
+    end
+
+    candidates_scope.map do |match|
+      Transfer.new(
+        inflow_transaction_id: match.inflow_transaction_id,
+        outflow_transaction_id: match.outflow_transaction_id,
+      )
+    end
+  end
+
+  private
+    def family_matches_scope
+      self.entry.account.family.transfer_match_candidates
+    end
+end