feat(postgres): add extension management

crates/dbx-core/src/database_export.rs

@@ -1300,8 +1300,13 @@ pub async fn export_database_sql_core(
             PostgresExtensionMembers::default()
         };
     let postgres_extensions = if request.include_structure && matches!(db_type, DatabaseType::Postgres) {
-        match crate::schema::list_extensions_core(state, &request.connection_id, &request.database, &request.schema)
-            .await
+        match crate::schema::list_extensions_core(
+            state,
+            &request.connection_id,
+            &request.database,
+            Some(&request.schema),
+        )
+        .await
         {
             Ok(extensions) => extensions
                 .into_iter()