fix(dameng): use ALTER TABLE constraints for unique indexes

apps/desktop/src/types/database.ts

@@ -554,6 +554,12 @@ export interface IndexInfo {
   key_is_expression?: boolean[] | null;
   /** Parallel to `columns`: operator class name for each key column (PostgreSQL), if non-default. */
   column_opclasses?: (string | null)[] | null;
+  /**
+   * True when the index is the object behind a PRIMARY KEY / UNIQUE constraint rather than a
+   * standalone index. Carried back to the backend inside the index draft's `original` snapshot:
+   * Dameng only accepts `ALTER TABLE ... ADD/DROP CONSTRAINT` for those indexes.
+   */
+  constraint_backed?: boolean | null;
 }
 
 export interface ReferenceKeyInfo {