feat: integrate platform backend and application interfaces

server/migrations/0020_v1_recharge_order_idempotency_scope.sql

@@ -0,0 +1,5 @@
+ALTER TABLE IF EXISTS recharge_orders
+  DROP CONSTRAINT IF EXISTS recharge_orders_idempotency_key_key;
+
+CREATE UNIQUE INDEX IF NOT EXISTS recharge_orders_user_idempotency_idx
+  ON recharge_orders(user_id, idempotency_key);