Add app blueprint generation flow

RuoYi-Vue/sql/front_app_blueprint.sql

@@ -0,0 +1,17 @@
+set @front_app_blueprint_exists := (
+  select count(1)
+  from information_schema.columns
+  where table_schema = database()
+    and table_name = 'front_project'
+    and column_name = 'app_blueprint'
+);
+
+set @front_app_blueprint_sql := if(
+  @front_app_blueprint_exists = 0,
+  'alter table front_project add column app_blueprint longtext comment ''应用蓝图草稿JSON'' after preview_status',
+  'select ''front_project.app_blueprint already exists'''
+);
+
+prepare front_app_blueprint_stmt from @front_app_blueprint_sql;
+execute front_app_blueprint_stmt;
+deallocate prepare front_app_blueprint_stmt;