feat(scenario): add scenario and scenario step CRUD module

- add ScenarioEntity and ScenarioStepEntity with cascade delete
- step fields: type (login|exec), sessionName (required), execCode, validateCode
- login steps create a named session; exec steps consume it by sessionName
- full CRUD controller under /scenarios and /scenarios/:id/steps
- paginated GET /scenarios with page/limit query params returning { data, total, page, limit }
- register ScenarioModule and entities in AppModule

src/scenario/dto/update-scenario.dto.ts

@@ -0,0 +1,10 @@
+import { ApiPropertyOptional } from '@nestjs/swagger';
+import { IsOptional, IsString, IsNotEmpty } from 'class-validator';
+
+export class UpdateScenarioDto {
+  @ApiPropertyOptional({ example: 'Updated scenario name' })
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  name?: string;
+}