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/scenario-step.entity.ts

@@ -0,0 +1,45 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+  UpdateDateColumn,
+  ManyToOne,
+  JoinColumn,
+} from 'typeorm';
+import { ScenarioEntity } from './scenario.entity';
+
+export type StepType = 'login' | 'exec';
+
+@Entity('scenario_steps')
+export class ScenarioStepEntity {
+  @PrimaryGeneratedColumn()
+  id: number;
+
+  @Column()
+  scenarioId: number;
+
+  @ManyToOne(() => ScenarioEntity, (scenario) => scenario.steps, {
+    onDelete: 'CASCADE',
+  })
+  @JoinColumn({ name: 'scenarioId' })
+  scenario: ScenarioEntity;
+
+  @Column({ type: 'text' })
+  type: StepType;
+
+  @Column({ type: 'text' })
+  sessionName: string;
+
+  @Column({ type: 'text', nullable: true })
+  execCode: string | null;
+
+  @Column({ type: 'text', nullable: true })
+  validateCode: string | null;
+
+  @CreateDateColumn()
+  createdAt: Date;
+
+  @UpdateDateColumn()
+  updatedAt: Date;
+}