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>

db/migrate/20260117200000_add_tax_treatment_to_cryptos.rb

@@ -0,0 +1,5 @@
+class AddTaxTreatmentToCryptos < ActiveRecord::Migration[7.2]
+  def change
+    add_column :cryptos, :tax_treatment, :string, default: "taxable", null: false
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2026_01_16_090336) do
+ActiveRecord::Schema[7.2].define(version: 2026_01_17_200000) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -256,6 +256,7 @@ ActiveRecord::Schema[7.2].define(version: 2026_01_16_090336) do
     t.datetime "updated_at", null: false
     t.jsonb "locked_attributes", default: {}
     t.string "subtype"
+    t.string "tax_treatment", default: "taxable", null: false
   end
 
   create_table "data_enrichments", id: :uuid, default: -> { "gen_random_uuid()" }, force: :cascade do |t|