Add tax treatment classification for investment accounts with international support (#693)

* Add tax treatment support for accounts, investments, and cryptos

* Replace hardcoded region labels with I18n translations

* Add I18n support for subtype labels with fallback to hardcoded values

* fixed schema

---------

Co-authored-by: luckyPipewrench <luckypipewrench@proton.me>

app/models/concerns/accountable.rb

@@ -31,11 +31,17 @@ module Accountable
     end
 
     # Given a subtype, look up the label for this accountable type
+    # Uses i18n with fallback to hardcoded SUBTYPES values
     def subtype_label_for(subtype, format: :short)
       return nil if subtype.nil?
 
       label_type = format == :long ? :long : :short
-      self::SUBTYPES[subtype]&.fetch(label_type, nil)
+      fallback = self::SUBTYPES.dig(subtype, label_type)
+
+      I18n.t(
+        "#{name.underscore.pluralize}.subtypes.#{subtype}.#{label_type}",
+        default: fallback
+      )
     end
 
     # Convenience method for getting the short label

app/models/concerns/tax_treatable.rb

@@ -0,0 +1,26 @@
+module TaxTreatable
+  extend ActiveSupport::Concern
+
+  # Delegates tax treatment to the accountable (Investment or Crypto)
+  # Returns nil for account types that don't support tax treatment
+  def tax_treatment
+    return nil unless accountable.respond_to?(:tax_treatment)
+    accountable.tax_treatment&.to_sym
+  end
+
+  # Returns the i18n label for the tax treatment
+  def tax_treatment_label
+    return nil unless tax_treatment
+    I18n.t("accounts.tax_treatments.#{tax_treatment}")
+  end
+
+  # Returns true if the account has tax advantages (deferred, exempt, or advantaged)
+  def tax_advantaged?
+    tax_treatment.in?(%i[tax_deferred tax_exempt tax_advantaged])
+  end
+
+  # Returns true if gains in this account are taxable
+  def taxable?
+    tax_treatment == :taxable || tax_treatment.nil?
+  end
+end