feat(scenario): add scheduler, cancelled step status, and runs list endpoint

- install @nestjs/schedule and register ScheduleModule in AppModule
- add ScenarioSchedulerService with two 1s interval jobs:
  - activatePendingRuns: flips pending runs to in_progress
  - processPendingStepRuns: executes next pending step run (login or exec),
    runs optional validateCode, advances or fails the run accordingly
- on step pass: next waiting step becomes pending; last step pass flips run to pass
- on step fail: remaining steps set to cancelled, run flipped to fail
- add cancelled to RunStepStatus union
- add GET /scenarios/:id/runs with pagination and optional ?status= filter

src/scenario/dto/runs-query.dto.ts

@@ -0,0 +1,28 @@
+import { ApiPropertyOptional } from '@nestjs/swagger';
+import { Type } from 'class-transformer';
+import { IsIn, IsInt, IsOptional, Min } from 'class-validator';
+import { RunStatus } from '../scenario-run.entity';
+
+export class RunsQueryDto {
+  @ApiPropertyOptional({ example: 1, default: 1 })
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt()
+  @Min(1)
+  page?: number = 1;
+
+  @ApiPropertyOptional({ example: 20, default: 20 })
+  @IsOptional()
+  @Type(() => Number)
+  @IsInt()
+  @Min(1)
+  limit?: number = 20;
+
+  @ApiPropertyOptional({
+    enum: ['pending', 'in_progress', 'pass', 'fail'],
+    description: 'Filter by run status',
+  })
+  @IsOptional()
+  @IsIn(['pending', 'in_progress', 'pass', 'fail'])
+  status?: RunStatus;
+}