feat(expenses): add beloPrice and usdcEquivalent fields to Expense model and update related logic

apps/backend/prisma/migrations/20260608223915_add_belo_quote_to_expenses/migration.sql

@@ -0,0 +1,3 @@
+-- AlterTable
+ALTER TABLE "expenses" ADD COLUMN     "beloPrice" MONEY,
+ADD COLUMN     "usdcEquivalent" DECIMAL(12,6);