feat(scenario): add scenario runs, run steps, and step ordering

- add ScenarioRunEntity (pending|in_progress|pass|fail) and ScenarioRunStepEntity (waiting|pending|in_progress|pass|fail)
- add POST /scenarios/:id/run — creates run with first step pending, rest waiting
- add order field to ScenarioStepEntity and ScenarioRunStepEntity for deterministic sequential execution
- findOne and createRun now sort steps/stepRuns by order ASC

src/scenario/scenario.controller.ts

@@ -111,4 +111,14 @@ export class ScenarioController {
   ) {
     return this.scenarioService.removeStep(id, stepId);
   }
+
+  // ── Runs ──────────────────────────────────────────────────────────────────
+
+  @Post(':id/run')
+  @ApiOperation({ summary: 'Create a new run for a scenario' })
+  @ApiResponse({ status: 201, description: 'Run created with step runs' })
+  @ApiResponse({ status: 404, description: 'Scenario not found' })
+  createRun(@Param('id', ParseIntPipe) id: number) {
+    return this.scenarioService.createRun(id);
+  }
 }