Balance sheet cache layer, non-blocking sync UI (#2356)

* Balance sheet cache layer with cache-busting

* Update family cache timestamps during Sync

* Less blocking sync loaders

* Consolidate family data caching key logic

* Fix turbo stream broadcasts

* Remove dev delay

* Add back account group sorting

db/migrate/20250610181219_add_sync_timestamps_to_family.rb

@@ -0,0 +1,6 @@
+class AddSyncTimestampsToFamily < ActiveRecord::Migration[7.2]
+  def change
+    add_column :families, :latest_sync_activity_at, :datetime, default: -> { "CURRENT_TIMESTAMP" }
+    add_column :families, :latest_sync_completed_at, :datetime, default: -> { "CURRENT_TIMESTAMP" }
+  end
+end