Add non-custom currencies per group

prisma/migrations/20250405152338_add_group_currency_code/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "Group" ADD COLUMN     "currencyCode" TEXT;

prisma/schema.prisma

@@ -16,6 +16,7 @@ model Group {
   name         String
   information  String?       @db.Text
   currency     String        @default("$")
+  currencyCode String? 
   participants Participant[]
   expenses     Expense[]
   activities   Activity[]